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docs/depolarization/depolarization.rst
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| 1 **Single Calculus Chain ** | |
| 2 | |
| 3 **version: 4.0** | |
| 4 | |
| 5 **date: Date (fixed)** | |
| 6 | |
| 7 **DRAFT** | |
| 8 | |
| 9 This document describes the main changes implemented in the SCC v4.0 | |
| 10 with respect to what already provided in the SCC v3.11. It will be also | |
| 11 reported the modifications the users need to perform to run the new | |
| 12 version of SCC. | |
| 13 | |
| 14 Table of Contents | |
| 15 | |
| 16 1. Particle Linear Depolarization Ratio Implementation 3 | |
| 17 | |
| 18 1.1 Background 3 | |
| 19 | |
| 20 1.2 Polarization calibration 4 | |
| 21 | |
| 22 1.3 SCC procedure to calculate the PLDRP 4 | |
| 23 | |
| 24 2.Changes of the SCC input format 8 | |
| 25 | |
| 26 3.Real Example 10 | |
| 27 | |
| 28 3.1 Modification of polarization channel parameters 10 | |
| 29 | |
| 30 3.2 Definition of new calibration configuration and product 12 | |
| 31 | |
| 32 3.3 Definition of “Raman/Elastic backscatter and linear depolarization | |
| 33 ratio” 16 | |
| 34 | |
| 35 Particle Linear Depolarization Ratio Implementation | |
| 36 =================================================== | |
| 37 | |
| 38 The most important improvement included in the SCC v4.0 is the | |
| 39 implementation of a new optical product which is the particle linear | |
| 40 depolarization ratio. | |
| 41 | |
| 42 **Background** | |
| 43 -------------- | |
| 44 | |
| 45 The calculation of the volume linear depolarization ratio profile | |
| 46 (*VLDR*) and particle linear depolarization ratio profile (*PLDR*) needs | |
| 47 two different steps: | |
| 48 | |
| 49 1. the calibration of the polarization sensitive lidar channels; | |
| 50 | |
| 51 2. the calculation of the *VLDR* or *PLDR* itself. | |
| 52 | |
| 53 The SCC allows the user to make both the above points. In particular the | |
| 54 calibration step is made by a completely new module called | |
| 55 **scc\_calibrator** which computes the *apparent calibration factor* | |
| 56 h\ :sup:`\*` out of the pre-processed data provided by the standard | |
| 57 **ELPP** (Earlinet Lidar Pre-Processor) module and it records it in the | |
| 58 SCC database (SCC\_DB). Once logged into the SCC\_DB this factor can be | |
| 59 used whenever it is necessary. | |
| 60 | |
| 61 The raw lidar calibration measurements should be put in a NetCDF file | |
| 62 which has the same structure as the “standard” raw SCC NetCDF input file | |
| 63 (for more details see sections 2 and 3.2). | |
| 64 | |
| 65 New signal types have been introduced to take into account special | |
| 66 channel configurations used for calibration purposes. | |
| 67 | |
| 68 Moreover new product types for both calibration and *PLDR* calculation | |
| 69 have been defined. As, in principle, it is possible to calculate the | |
| 70 *PLDR* only when the aerosol backscatter coefficient profile is | |
| 71 available the following new products have been defined: | |
| 72 | |
| 73 1. *Linear polarization calibration (factor* h) *(product\_type\_id=6);* | |
| 74 | |
| 75 2. *Raman backscatter and linear depolarization ratio | |
| 76 (product\_type\_id=7);* | |
| 77 | |
| 78 3. *Elastic backscatter and linear depolarization ratio | |
| 79 (product\_type\_id=8).* | |
| 80 | |
| 81 The first product in the above list is used only for calibration while | |
| 82 the other two are used for the calculation of *PLDR*. Basically, in most | |
| 83 of the cases, the products 2 and 3 are equivalent to the corresponding | |
| 84 backscatter product types with the exception that also the following new | |
| 85 variables are available: | |
| 86 | |
| 87 double VolumeDepol(Length) ; | |
| 88 | |
| 89 double ErrorVolumeDepol(Length) ; | |
| 90 | |
| 91 ErrorVolumeDepol:long\_name = "absolute error of VolumeDepol" ; | |
| 92 | |
| 93 double ParticleDepol(Length) ; | |
| 94 | |
| 95 double ErrorParticleDepol(Length) ; | |
| 96 | |
| 97 ErrorParticleDepol:long\_name = "absolute error of ParticleDepol" ; | |
| 98 | |
| 99 **Polarization calibration** | |
| 100 ---------------------------- | |
| 101 | |
| 102 An important point is the definition of reliable *PLDR* calibration | |
| 103 procedures. Within EARLINET the following calibration procedures are | |
| 104 currently used: | |
| 105 | |
| 106 a) Rayleigh calibration; | |
| 107 | |
| 108 b) +45 calibration method, or D90 calibration method (made by +45 and | |
| 109 -45 measurements); | |
| 110 | |
| 111 c) 3 signals (total, cross and parallel). | |
| 112 | |
| 113 It is well known that method a) could produce easily large errors on | |
| 114 *PLDR* which cannot be controlled. For this reason only the methods b) | |
| 115 and c) can be used to provide reliable polarization calibrations and so | |
| 116 only those methods will be implemented in the SCC. | |
| 117 | |
| 118 For what it concerns the method c) it, basically, requires to solve the | |
| 119 equation: | |
| 120 | |
| 121 in two different of atmospheric layers with considerably different | |
| 122 *VLDR*. So to calibrate in this way the implementation of automatic | |
| 123 layer identification in the SCC is required. As at moment this feature | |
| 124 is not yet available within the SCC *ONLY* the method b) is considered. | |
| 125 | |
| 126 SCC procedure to calculate the PLDRP | |
| 127 ------------------------------------ | |
| 128 | |
| 129 According to what mentioned before the SCC calculates the *PLDR* through | |
| 130 the following steps: | |
| 131 | |
| 132 1. The user needs to create a new system configuration in the SCC\_DB | |
| 133 including only lidar channels used for the calibration. One (or more) | |
| 134 *Linear polarization calibration (product\_type\_id=6)* product | |
| 135 should be associated to this new configuration (see section 3.2 for | |
| 136 more details); | |
| 137 | |
| 138 2. This new system configuration should contain only the polarization | |
| 139 channels in the configuration used for the calibration (for example | |
| 140 rotated in the polarization plane of +45 degrees). A channel in | |
| 141 calibration measurement configuration should have a *DIFFERENT* | |
| 142 channel ID from the channel ID corresponding to the same channel in | |
| 143 standard measurement configuration. For example, if a system has two | |
| 144 polarization channels which in standard measurement configuration | |
| 145 correspond to the channel ID=1 and 2 respectively, the same physical | |
| 146 channels under calibration measurement configuration should | |
| 147 correspond to different channel IDs (let's say ID=3 and 4 for the +45 | |
| 148 degrees polarization rotated channels and ID=5 and 6 for the -45 | |
| 149 degrees polarization rotated ones in case D90 calibration method is | |
| 150 used). Moreover, the polarization channels should be labeled | |
| 151 correctly using the new signal types available (*+45elPT, +45elPR, | |
| 152 -45elPT, -45elPR, +45elPTnr, +45elPTfr, +45elPRnr, +45elPRfr, | |
| 153 -45elPTnr, -45elPTfr, -45elPRnr, -45elPRfr).* For more details see | |
| 154 section 3.2; | |
| 155 | |
| 156 3. In SCC v4.0 the polarization channels are *NOT* labeled on the base | |
| 157 of their polarization state (as it was done in the SCC v3.11) but | |
| 158 *ALWAYS* as transmitted and reflected channels. So the channels that | |
| 159 in SCC v3.11 were labeled as *elCP, elCPnr, elCPfr, elPP, elPPnr | |
| 160 elPPfr* will be labeled in SCC v4.0 as *elPR, elPRnr elPRfr elPT, | |
| 161 elPTnr elPTfr* where the letter *T* stands from transmitted and the | |
| 162 letter *R* for reflected. | |
| 163 | |
| 164 **WARNING:** In switching from the SCC v3.11 to SCC v4.0 the following | |
| 165 modifications have been made on *ALL* channels of *ALL* registered | |
| 166 configurations: | |
| 167 | |
| 168 *elPP→elPR* | |
| 169 | |
| 170 *elCP→elPT* | |
| 171 | |
| 172 *elPPnr→elPRnr* | |
| 173 | |
| 174 *elPPfr→ elPRfr* | |
| 175 | |
| 176 *elCPnr→ elPTnr* | |
| 177 | |
| 178 *elCPfr→ elPTfr* | |
| 179 | |
| 180 Please be sure these modifications reflect to your actual lidar setup | |
| 181 (cross channels are transmitted and parallel channels are reflected); | |
| 182 | |
| 183 1. The user needs to submit a file (same format as raw SCC input file) | |
| 184 containing the raw data for the lidar channels defined at the point 1 | |
| 185 (see section 3.2 for more details); | |
| 186 | |
| 187 2. The file at point 2 is pre-processed by **ELPP** module which applies | |
| 188 the standard pre-processing procedures applied to “standard” lidar | |
| 189 data; | |
| 190 | |
| 191 3. The pre-processed files are then processed by the new modules | |
| 192 **scc\_calibrator** which calculates h\ :sup:`\*` *the apparent | |
| 193 calibration factor* and logs it into the SCC\_DB; | |
| 194 | |
| 195 4. The user needs to create a new system configuration in the SCC\_DB | |
| 196 (which should be different from the one used for the calibration) and | |
| 197 associate it the new product *Raman backscatter and linear | |
| 198 depolarization ratio (product\_type\_id=7)* or *Elastic backscatter | |
| 199 and linear depolarization ratio (product\_type\_id=8).* Alternatively | |
| 200 the calculation of those products can be added to an already existing | |
| 201 lidar configuration as long as it is different from the calibration | |
| 202 one; | |
| 203 | |
| 204 5. The product defined at point 5 should be linked to the product | |
| 205 containing the polarization calibration (defined at point 1) in a way | |
| 206 that the *apparent calibration factor* can be selected from the | |
| 207 SCC\_DB (see section 3.3 and in particular figure 3.4); | |
| 208 | |
| 209 6. The user needs to submit another SCC raw data file containing the | |
| 210 “standard” measurements; | |
| 211 | |
| 212 7. Finally **ELPP** and **ELDA** will produce a b-file containing | |
| 213 backscatter coefficient profile and *PLDR*. In particular this | |
| 214 calculation is made in two different steps: from the pre-processed | |
| 215 lidar polarization signals, and taking into account the *apparent | |
| 216 calibration factor* and the *calibration factor correction K* | |
| 217 (defined as option of *Linear polarization calibration* product\ *)* | |
| 218 written into the SCC\_DB, an “apparent” *VLDR* *d\ :sup:`\*`* is | |
| 219 calculated. Even if *d\ :sup:`\*`* is a calibrated quantity it can be | |
| 220 still affected by possible systematic errors due to not perfect | |
| 221 optics or alignment of the system; | |
| 222 | |
| 223 8. To take into account these errors a corrected *VLDR* (*d)* is | |
| 224 calculated using the *polarization cross-talk correction parameters* | |
| 225 *G* and *H* calculated on the base of Müller matrix formalism. These | |
| 226 cross-talk correction parameters (*G* and *H*) are stored in the | |
| 227 SCC\_DB for each lidar channels (see section 3.1 in particular figure | |
| 228 3.2). Finally the *PLDR* is calculated using the backscatter | |
| 229 coefficient profile and the molecular LDRP calculated by ELPP | |
| 230 considering the center wavelength and bandwidth of the channels | |
| 231 interference filter. | |
| 232 | |
| 233 The *apparent calibration factor* h\ :sup:`\*` is calculated by the | |
| 234 **scc\_calibrator** module as the geometrical mean of the ratio of the | |
| 235 +/-45 degrees reflected to the +/- 45 degrees transmitted signals within | |
| 236 an altitude calibration range defined by the users in the raw data input | |
| 237 files. | |
| 238 | |
| 239 In case of +45 calibration method h\ :sup:`\*` is calculated by: | |
| 240 | |
| 241 (1.1) | |
| 242 | |
| 243 While in case of D90 calibration method: | |
| 244 | |
| 245 (1.2) | |
| 246 | |
| 247 **ELDA** module calculates the “apparent” *VLDR*: | |
| 248 | |
| 249 (1.3) | |
| 250 | |
| 251 the *VLDR* | |
| 252 | |
| 253 (1.4) | |
| 254 | |
| 255 and the *PLDR* | |
| 256 | |
| 257 (1.5) | |
| 258 | |
| 259 where: | |
| 260 | |
| 261 - h\ :sup:`\*` is the *apparent calibration factor* calculated by | |
| 262 **scc\_calibrator** | |
| 263 | |
| 264 - *K* is the *calibration factor correction* defined as polarization | |
| 265 product option | |
| 266 | |
| 267 - *I\ :sub:`T`* and I\ *:sub:`R`* are the transmitted and the reflected | |
| 268 signals in the polarization detection set-up | |
| 269 | |
| 270 - *G\ :sub:`T,R`* and *H\ :sub:`T,R`* are *polarization cross-talk | |
| 271 correction parameters* for the transmitted and reflected signals used | |
| 272 to correct for systematic errors. Both these factors are defined in | |
| 273 the SCC\_DB for each lidar channel. | |
| 274 | |
| 275 - *d\ :sub:`m`* is the molecular linear depolarization ratio calculated | |
| 276 by ELPP | |
| 277 | |
| 278 - *R* is the backscatter ratio | |
| 279 | |
| 280 Please note once again that the polarization channels are described in | |
| 281 terms of transmitted and reflected signals. This means that according to | |
| 282 different lidar instrumental configurations, the transmitted or the | |
| 283 reflected channel can contain total, perpendicular or parallel polarized | |
| 284 signals. | |
| 285 | |
| 286 In order to retrieve the backscatter profile the total signal must be | |
| 287 obtained combining the transmitted and reflected polarized signals. The | |
| 288 following formula is used: | |
| 289 | |
| 290 (1.6) | |
| 291 | |
| 292 The formulas above are general and can be adapted to all possible | |
| 293 polarization lidar configurations selecting the right polarization | |
| 294 cross-talk correction parameters (see Table 1.1). | |
| 295 | |
| 296 Let's suppose, for example, we have the perpendicular polarized lidar | |
| 297 signal on the transmitted channel and the parallel polarized on | |
| 298 reflected channel. For an ideal system (no diattenuation and cross-talk) | |
| 299 we have: | |
| 300 | |
| 301 If, on the other hands, we have the perpendicular polarized lidar signal | |
| 302 on reflected channel and the total polarized on the transmitted for and | |
| 303 ideal system we have: | |
| 304 | |
| 305 **Table 1.1:** Polarization cross-talk correction parameters for ideal | |
| 306 systems | |
| 307 | |
| 308 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 309 | Laser polarization | Detected in lidar channel | | |
| 310 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 311 | | Transmitted | Reflected | | |
| 312 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 313 | | *G\ :sub:`T`* | *H\ :sub:`T`* | *G\ :sub:`R`* | *H\ :sub:`R`* | | |
| 314 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 315 | total | 1 | 0 | 1 | 0 | | |
| 316 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 317 | parallel | 1 | 1 | 1 | 1 | | |
| 318 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 319 | cross | 1 | -1 | 1 | -1 | | |
| 320 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ | |
| 321 | |
| 322 The *apparent calibration factor* (h:sup:`\*`), *the calibration factor | |
| 323 correction* (*K*) and the *polarization cross-talk correction | |
| 324 parameters* are stored by **ELPP** module in the intermediate NetCDF | |
| 325 files using the following variables: | |
| 326 | |
| 327 - *Polarization\_Channel\_Gain\_Factor (apparent calibration factor* – | |
| 328 h\ :sup:`\*`) | |
| 329 | |
| 330 - *Polarization\_Channel\_Gain\_Factor\_Correction (calib. factor | |
| 331 corr.* – *K*) | |
| 332 | |
| 333 - *G\_T* | |
| 334 | |
| 335 - *H\_T* | |
| 336 | |
| 337 - *G\_R* | |
| 338 | |
| 339 - *H\_R* | |
| 340 | |
| 341 Finally new usecases have been defined to take into account all the | |
| 342 possible lidar configurations. The details on that are provided as a | |
| 343 separate file. | |
| 344 | |
| 345 Changes of the SCC input format | |
| 346 =============================== | |
| 347 | |
| 348 The following minor changes have been applied to raw SCC data format: | |
| 349 | |
| 350 1. The optional variable *ID\_Range* has been *REMOVED*; | |
| 351 | |
| 352 2. The *OPTIONAL* variable *int Signal\_Type(channels)* has been added. | |
| 353 The possible values are the same available in the SCC\_DB: | |
| 354 | |
| 355 0 *→* elT | |
| 356 | |
| 357 1 *→* elTnr | |
| 358 | |
| 359 2 *→* elTfr | |
| 360 | |
| 361 3 *→* vrRN2 | |
| 362 | |
| 363 4 *→* vrRN2nr | |
| 364 | |
| 365 5 *→* vrRN2fr | |
| 366 | |
| 367 6 *→* elPR | |
| 368 | |
| 369 7 *→* elPT | |
| 370 | |
| 371 8 *→* pRRlow | |
| 372 | |
| 373 9 *→* pRRhigh | |
| 374 | |
| 375 10 *→* elPRnr | |
| 376 | |
| 377 11 *→* elPRfr | |
| 378 | |
| 379 12 *→* elPTnr | |
| 380 | |
| 381 13 *→* elPTfr | |
| 382 | |
| 383 14 *→* vrRH2O | |
| 384 | |
| 385 15 *→* pRRhighnr | |
| 386 | |
| 387 16 *→* pRRhighfr | |
| 388 | |
| 389 17 *→* pRRlownr | |
| 390 | |
| 391 18 *→* pRRlowfr | |
| 392 | |
| 393 19 *→* vrRH2Onr | |
| 394 | |
| 395 20 *→* vrRH2Ofr | |
| 396 | |
| 397 21 *→* elTunr | |
| 398 | |
| 399 *22 → +45elPT* | |
| 400 | |
| 401 *23 → +45elPR* | |
| 402 | |
| 403 *24 → -45elPT* | |
| 404 | |
| 405 *25 → -45elPR* | |
| 406 | |
| 407 *26 → +45elPTnr* | |
| 408 | |
| 409 *27 → +45elPTfr* | |
| 410 | |
| 411 *28 → +45elPRnr* | |
| 412 | |
| 413 *29 → +45elPRfr* | |
| 414 | |
| 415 *30 → -45elPTnr* | |
| 416 | |
| 417 *31 → -45elPTfr* | |
| 418 | |
| 419 *32 → -45elPRnr* | |
| 420 | |
| 421 *33 → -45elPRfr* | |
| 422 | |
| 423 **WARNING:** It this variable is found in the SCC input file the | |
| 424 corresponding settings in the SCC database will be *overwritten*. Unless | |
| 425 you don't have any valid reason to overwrite the database value this | |
| 426 variable should not be used. | |
| 427 | |
| 428 1. The variables: | |
| 429 | |
| 430 *double Pol\_Calib\_Range\_Min(channels)* | |
| 431 | |
| 432 *double Pol\_Calib\_Range\_Max(channels) * | |
| 433 | |
| 434 have been added. Both these variable are *mandatory* for any calibration | |
| 435 raw dataset. | |
| 436 | |
| 437 These variable should be included only the polarization calibration | |
| 438 measurements and should specify the altitude range (meters) in which the | |
| 439 polarization calibration should be made. For more details see section | |
| 440 3.3; | |
| 441 | |
| 442 1. The variable *Depolarization\_Factor* has been *removed*. | |
| 443 | |
| 444 The SCC v3.11 used this variable to get polarization calibration factor | |
| 445 for the calculation of the total signal out of cross and parallels ones. | |
| 446 As the SCC v4.0 is able to calculate the same parameter by itself, the | |
| 447 use of this variable is *NOT* possible anymore. The recommended way to | |
| 448 get a valid and quality assured depolarization calibration factor is to | |
| 449 submit to the SCC v4.0 a polarization calibration dataset and let the | |
| 450 SCC to calculate such factor. | |
| 451 | |
| 452 To make this change more smooth and to provide the users with the | |
| 453 possibility to continue to analyze their data with the SCC v4.0 even if | |
| 454 a calibration dataset has not been submitted yet, it will be possible | |
| 455 for a *LIMITED* period of time to submit the calibration constant via | |
| 456 the SCC web interface. The SCC will keep track of the used calibration | |
| 457 method (automatic or manual). | |
| 458 | |
| 459 **WARNING:** After this transition period *only* automatic calibration | |
| 460 will be allowed! | |
| 461 | |
| 462 1. The new *optional* variable: | |
| 463 | |
| 464 *string channel\_string\_ID(channels)* | |
| 465 | |
| 466 has been introduced. | |
| 467 | |
| 468 Starting from SCC v4.0 the lidar channel can be identified not only by | |
| 469 using integers (as it happened until SCC v3.11) but also by using | |
| 470 strings. | |
| 471 | |
| 472 The procedure implemented in the SCC v4.0 to recognize the lidar channel | |
| 473 within the raw lidar data is fully backward compatible (old format files | |
| 474 are accepted as they are by SCC v4.0). | |
| 475 | |
| 476 **WARNING:** Please note that the definition of the new string variable | |
| 477 requires netCDF-4 format! The type *string* is not supported in netCDF-3 | |
| 478 format! | |
| 479 | |
| 480 Real Example | |
| 481 ============ | |
| 482 | |
| 483 This section describes all the practical steps the users need to follow | |
| 484 to switch from SCC v3.11 to new SCC v4.0. | |
| 485 | |
| 486 **IMPORTANT:** | |
| 487 | |
| 488 If your lidar system is not equipped with any polarization channels *NO* | |
| 489 changes are required. In this case, the SCC v4.0 should work using the | |
| 490 same input files and the same database configurations you have used with | |
| 491 the SCC v3.11. Anyway as in the SCC v4.0 several bugs have been fixed, | |
| 492 it is recommended to re-run all the measurement IDs you have submitted. | |
| 493 For doing that you just need to reprocess all your data without the need | |
| 494 to submit raw data files already uploaded on the server. | |
| 495 | |
| 496 The practical example reported below describes the modifications | |
| 497 required to use the SCC v4.0 for lidar systems equipped with | |
| 498 polarization channels. | |
| 499 | |
| 500 Modification of polarization channel parameters | |
| 501 ----------------------------------------------- | |
| 502 | |
| 503 In what it follows it is assumed you already have registered one or more | |
| 504 lidar configurations in the SCC database and that such configurations | |
| 505 have been already used to produce optical products (aerosol extinction | |
| 506 and/or backscatter coefficients) by means of the SCC v3.11. | |
| 507 | |
| 508 Let's assume your 3+2 system is registered in the SCC database and the | |
| 509 settings used by the SCC v3.11 are the ones summarized in table 3.1. | |
| 510 | |
| 511 **Table 3.1:** Example of configuration in SCC v3.11 | |
| 512 | |
| 513 +----------------+--------------+----------------+-------------+-----------+ | |
| 514 | Channel Name | Channel ID | Channel Type | nighttime | daytime | | |
| 515 +----------------+--------------+----------------+-------------+-----------+ | |
| 516 | 355 | 1 | elT | | | | |
| 517 +----------------+--------------+----------------+-------------+-----------+ | |
| 518 | 387 | 2 | vrRN2 | | | | |
| 519 +----------------+--------------+----------------+-------------+-----------+ | |
| 520 | 532 cross | 3 | elCP | | | | |
| 521 +----------------+--------------+----------------+-------------+-----------+ | |
| 522 | 532 parallel | 4 | elPP | | | | |
| 523 +----------------+--------------+----------------+-------------+-----------+ | |
| 524 | 607 | 5 | vrRN2 | | | | |
| 525 +----------------+--------------+----------------+-------------+-----------+ | |
| 526 | 1064 | 6 | elT | | | | |
| 527 +----------------+--------------+----------------+-------------+-----------+ | |
| 528 | |
| 529 We assume there are 2 system configurations called “nighttime” and | |
| 530 “daytime”. The nighttime configuration contains all the available lidar | |
| 531 channels (in order to calculate, for example, the aerosol extinction at | |
| 532 355 and 532nm and the aerosol backscatter at 355, 532 and 1064nm) while | |
| 533 in daytime conditions only elastic channels are used (only elastic | |
| 534 backscatter coefficients are generated). | |
| 535 | |
| 536 To make these settings working with SCC v4.0 it is needed to modify | |
| 537 *ONLY* the products properties involving the polarization channels (532 | |
| 538 cross and parallel). All the products not involving the polarization | |
| 539 channels *DO NOT* need any modification and should work in the SCC v4.0 | |
| 540 exactly as they did in SCC v3.11. In the example above the aerosol | |
| 541 extinction and backscatter coefficient at 355nm, the extinction at 532nm | |
| 542 as well as the backscatter coefficient at 1064nm do not required any | |
| 543 modification. Let's focus on the modifications needed for the | |
| 544 calculation of backscatter at 532nm. | |
| 545 | |
| 546 |image0| How to select signal types | |
| 547 | |
| 548 The first modification concerns the settings of the channel type for the | |
| 549 532 cross and 532 parallel polarization channels. Starting from SCC v4.0 | |
| 550 polarization channels are identified as transmitted and reflected | |
| 551 polarization channels and not on the base of their polarization state. | |
| 552 So suppose if we suppose the cross polarized channel is transmitted by a | |
| 553 polarizer beam splitter cube and the parallel is reflected the value | |
| 554 reported in table 3.1 should be modified as they appear in table 3.2. So | |
| 555 using the SCC web interface, the signal type of the 532 cross channel | |
| 556 should be changed from elCP to elPT and and in the same way the 532 | |
| 557 parallel channel should be changed from elPP to elPR (see figure 3.1). | |
| 558 | |
| 559 **Table 3.2:** The same of table 3.1 but with new channel types | |
| 560 introduced in SCC v4.0 | |
| 561 | |
| 562 +----------------+--------------+----------------+-------------+-----------+ | |
| 563 | Channel Name | Channel ID | Channel Type | nighttime | daytime | | |
| 564 +----------------+--------------+----------------+-------------+-----------+ | |
| 565 | 355 | 1 | elT | | | | |
| 566 +----------------+--------------+----------------+-------------+-----------+ | |
| 567 | 387 | 2 | vrRN2 | | | | |
| 568 +----------------+--------------+----------------+-------------+-----------+ | |
| 569 | 532 cross | 3 | **elPT** | | | | |
| 570 +----------------+--------------+----------------+-------------+-----------+ | |
| 571 | 532 parallel | 4 | **elPR** | | | | |
| 572 +----------------+--------------+----------------+-------------+-----------+ | |
| 573 | 607 | 5 | vrRN2 | | | | |
| 574 +----------------+--------------+----------------+-------------+-----------+ | |
| 575 | 1064 | 6 | elT | | | | |
| 576 +----------------+--------------+----------------+-------------+-----------+ | |
| 577 | |
| 578 The other change about the polarization channels required to run the SCC | |
| 579 v4.0 is the definition of the polarization crosstalk parameters for all | |
| 580 the polarization channels available. Such parameters can be defined for | |
| 581 each polarization channel using the SCC web interface (see figure 3.2). | |
| 582 In particular among the channel parameters there is a new tab called | |
| 583 *Polarization crosstalk parameters* where it is possible to insert the | |
| 584 values from for the parameters *G* and *H* and the corresponding | |
| 585 statistical and systematic errors if available. In case you have | |
| 586 measured *G* and *H* for your polarization channels please insert the | |
| 587 corresponding values there. Otherwise you can insert the ideal values as | |
| 588 reported in table 1.1. | |
| 589 | |
| 590 |image1| *Polarization crosstalk parameters* tab in channel properties | |
| 591 (SCC v4.0). | |
| 592 | |
| 593 Definition of new calibration configuration and product | |
| 594 ------------------------------------------------------- | |
| 595 | |
| 596 In this section we will see how to set the polarization calibration | |
| 597 parameters: the calibration constant (called h\ :sup:`\*` in section | |
| 598 1.3) and the correction to calibration constant (called K in section | |
| 599 1.3). | |
| 600 | |
| 601 In order to provide such parameters you need to define a new system | |
| 602 configuration to be used *only* for calibration purposes. Such new | |
| 603 configuration should include the polarization channels in the | |
| 604 measurement configuration used for the calibration. Let's suppose we | |
| 605 want to use the D90 calibration method. | |
| 606 | |
| 607 In this case we need to define a new configuration (called for example | |
| 608 “depol\_calibration”) as reported in the table 3.3. As you can see the | |
| 609 configuration “depol\_calibration” includes 4 “new” channels. Actually | |
| 610 the channels “532 cross +45 degrees” (channel ID=10) and “532 cross -45 | |
| 611 degrees” (channel ID=12) refer to the same physical channel “532 cross” | |
| 612 reported with channel ID=3 in table 3.2. Anyway we need to define two | |
| 613 new channel IDs to identify the “532 cross” channel in the two | |
| 614 polarization rotated configurations (+45 and -45 degrees) needed to | |
| 615 apply the D90 calibration method. The same is true for the “532 | |
| 616 parallel” channel. The polarization rotated channels should be labeled | |
| 617 with the corresponding signal type as reported in table 3.3 (see figure | |
| 618 3.1). | |
| 619 | |
| 620 **Table 3.3:** Polarization calibration configurations assuming D90 | |
| 621 calibration method | |
| 622 | |
| 623 +----------------------------+--------------+----------------+----------------------+ | |
| 624 | Channel Name | Channel ID | Channel Type | depol\_calibration | | |
| 625 +----------------------------+--------------+----------------+----------------------+ | |
| 626 | 532 cross +45 degrees | 10 | +45elPT | | | |
| 627 +----------------------------+--------------+----------------+----------------------+ | |
| 628 | 532 parallel +45 degrees | 11 | +45elPR | | | |
| 629 +----------------------------+--------------+----------------+----------------------+ | |
| 630 | 532 cross -45 degrees | 12 | -45elPT | | | |
| 631 +----------------------------+--------------+----------------+----------------------+ | |
| 632 | 532 parallel -45 degrees | 13 | -45elPR | | | |
| 633 +----------------------------+--------------+----------------+----------------------+ | |
| 634 | |
| 635 Finally we should add to the configuration “depol\_calibration” a | |
| 636 product “\ *Linear polarization calibration”* to be used for the | |
| 637 calibration. According to the example given above and to the usecase | |
| 638 document attached we should use an usecase=4 for this example. | |
| 639 | |
| 640 Other “\ *Linear polarization calibration”* options to be specified are | |
| 641 reported in figure 3.3. The most important factor you should insert here | |
| 642 is the *Pol calibration correction factor* (K). The ideal value for this | |
| 643 parameter is 1. Anyway if you have measured the parameter K please fill | |
| 644 in the measured value and the corresponding measurement errors. | |
| 645 | |
| 646 |image2| Options for *Linear polarization calibration product*. | |
| 647 | |
| 648 As you can see it is possible to fill in only the K correction factor | |
| 649 and not the calibration constant h\ :sup:`\*`. | |
| 650 | |
| 651 Actually for a *LIMITED* period of time it will be possible to fill in | |
| 652 also the constant h\ :sup:`\*` using a temporary tab called | |
| 653 *Polarization calibration constant*. This has been done to provide the | |
| 654 users with the possibility to continue to use the SCC even if an | |
| 655 automatic calibration made by the SCC was not submitted yet. Anyway | |
| 656 after a transition period it will be *not* possible to provide | |
| 657 calibration constant using this procedure and the parameter h\ :sup:`\*` | |
| 658 can be calculated *ONLY* by the SCC as result of the submission of a | |
| 659 proper calibration raw input dataset. The format of this input file is | |
| 660 the same as the standard SCC input file. The only difference is that is | |
| 661 should contain calibration measurements instead of standard | |
| 662 measurements. Following our example, such file should contain the | |
| 663 measurement performed at +45 and -45 degrees at 532nm. Also the channel | |
| 664 IDs in the file should reflect the ones reported in table 3.3. | |
| 665 | |
| 666 Moreover this raw input file has to contain the variables: | |
| 667 | |
| 668 *double Pol\_Calib\_Range\_Min(channels)* | |
| 669 | |
| 670 *double Pol\_Calib\_Range\_Max(channels) * | |
| 671 | |
| 672 where to specify the altitude ranges in meters in which the polarization | |
| 673 calibration should be done. | |
| 674 | |
| 675 According to the table 3.3 this file should be something similar to: | |
| 676 | |
| 677 dimensions: | |
| 678 | |
| 679 channels = 4 ; | |
| 680 | |
| 681 nb\_of\_time\_scales = 1 ; | |
| 682 | |
| 683 points = 16380 ; | |
| 684 | |
| 685 scan\_angles = 1 ; | |
| 686 | |
| 687 time = UNLIMITED ; // (3 currently) | |
| 688 | |
| 689 variables: | |
| 690 | |
| 691 int channel\_ID(channels) ; | |
| 692 | |
| 693 double Background\_Low(channels) ; | |
| 694 | |
| 695 double Background\_High(channels) ; | |
| 696 | |
| 697 int id\_timescale(channels) ; | |
| 698 | |
| 699 double Laser\_Pointing\_Angle(scan\_angles) ; | |
| 700 | |
| 701 int Molecular\_Calc ; | |
| 702 | |
| 703 int Laser\_Pointing\_Angle\_of\_Profiles(time, nb\_of\_time\_scales) ; | |
| 704 | |
| 705 int Raw\_Data\_Start\_Time(time, nb\_of\_time\_scales) ; | |
| 706 | |
| 707 int Raw\_Data\_Stop\_Time(time, nb\_of\_time\_scales) ; | |
| 708 | |
| 709 int Laser\_Shots(time, channels) ; | |
| 710 | |
| 711 double Raw\_Lidar\_Data(time, channels, points) ; | |
| 712 | |
| 713 double Pressure\_at\_Lidar\_Station ; | |
| 714 | |
| 715 double Temperature\_at\_Lidar\_Station ; | |
| 716 | |
| 717 double Pol\_Calib\_Range\_Min(channels) ; | |
| 718 | |
| 719 double Pol\_Calib\_Range\_Max(channels) ; | |
| 720 | |
| 721 // global attributes: | |
| 722 | |
| 723 :System = "mysystem" ; | |
| 724 | |
| 725 :Longitude\_degrees\_east = 15.723771 ; | |
| 726 | |
| 727 :RawData\_Start\_Time\_UT = "220000" ; | |
| 728 | |
| 729 :RawData\_Start\_Date = "20130620" ; | |
| 730 | |
| 731 :Measurement\_ID = "20130620po00" ; | |
| 732 | |
| 733 :Altitude\_meter\_asl = 760. ; | |
| 734 | |
| 735 :RawData\_Stop\_Time\_UT = "230333" ; | |
| 736 | |
| 737 :Latitude\_degrees\_north = 40.601039 ; | |
| 738 | |
| 739 data: | |
| 740 | |
| 741 channel\_ID = 10, 11, 12, 13 ; | |
| 742 | |
| 743 Background\_Low = 30000, 30000, 30000, 30000 ; | |
| 744 | |
| 745 Background\_High = 50000, 50000, 50000, 50000 ; | |
| 746 | |
| 747 id\_timescale = 0, 0, 0, 0 ; | |
| 748 | |
| 749 Laser\_Pointing\_Angle = 0 ; | |
| 750 | |
| 751 Molecular\_Calc = 0 ; | |
| 752 | |
| 753 Laser\_Pointing\_Angle\_of\_Profiles = | |
| 754 | |
| 755 0, | |
| 756 | |
| 757 0, | |
| 758 | |
| 759 0 ; | |
| 760 | |
| 761 Raw\_Data\_Start\_Time = | |
| 762 | |
| 763 0, | |
| 764 | |
| 765 300, | |
| 766 | |
| 767 600 ; | |
| 768 | |
| 769 Raw\_Data\_Stop\_Time = | |
| 770 | |
| 771 210, | |
| 772 | |
| 773 510, | |
| 774 | |
| 775 810 ; | |
| 776 | |
| 777 Laser\_Shots = | |
| 778 | |
| 779 1200, 1200, 1200, 1200, | |
| 780 | |
| 781 1200, 1200, 1200, 1200, | |
| 782 | |
| 783 1200, 1200, 1200, 1200 ; | |
| 784 | |
| 785 Pressure\_at\_Lidar\_Station = 1010 ; | |
| 786 | |
| 787 Temperature\_at\_Lidar\_Station = 14 ; | |
| 788 | |
| 789 Pol\_Calib\_Range\_Min = 1000, 1000, 1000, 1000 ; | |
| 790 | |
| 791 Pol\_Calib\_Range\_Min = 2000, 2000, 2000, 2000 ; | |
| 792 | |
| 793 Raw\_Lidar\_Data = …...; | |
| 794 | |
| 795 The file above assume the following calibration measurements have been | |
| 796 done: | |
| 797 | |
| 798 1. First +45 degrees acquisition followed by a corresponding -45 degrees | |
| 799 acquisition | |
| 800 | |
| 801 a. Measurement at +45 degrees | |
| 802 | |
| 803 Start Time: 20130620 22:00:00 | |
| 804 | |
| 805 Stop Time: 20130620 22:01:00 | |
| 806 | |
| 807 Shots: 1200 | |
| 808 | |
| 809 a. Measurement at -45 degrees | |
| 810 | |
| 811 Start Time: 20130620 22:02:30 | |
| 812 | |
| 813 Stop Time: 20130620 22:03:30 | |
| 814 | |
| 815 Shots: 1200 | |
| 816 | |
| 817 1. Second +45 degrees acquisition followed by a corresponding -45 | |
| 818 degrees acquisition | |
| 819 | |
| 820 a. Measurement at +45 degrees | |
| 821 | |
| 822 Start Time: 20130620 22:05:00 | |
| 823 | |
| 824 Stop Time: 20130620 22:06:00 | |
| 825 | |
| 826 Shots: 1200 | |
| 827 | |
| 828 a. Measurement at -45 degrees | |
| 829 | |
| 830 Start Time: 20130620 22:07:30 | |
| 831 | |
| 832 Stop Time: 20130620 22:08:30 | |
| 833 | |
| 834 Shots: 1200 | |
| 835 | |
| 836 1. Third +45 degrees acquisition followed by a corresponding -45 degrees | |
| 837 acquisition | |
| 838 | |
| 839 a. Measurement at +45 degrees | |
| 840 | |
| 841 Start Time: 20130620 22:10:00 | |
| 842 | |
| 843 Stop Time: 20130620 22:11:00 | |
| 844 | |
| 845 Shots: 1200 | |
| 846 | |
| 847 a. Measurement at -45 degrees | |
| 848 | |
| 849 Start Time: 20130620 22:12:30 | |
| 850 | |
| 851 Stop Time: 20130620 22:13:30 | |
| 852 | |
| 853 Shots: 1200 | |
| 854 | |
| 855 As you can see there are 3 cycles of consecutive measurements at +45 and | |
| 856 -45 degrees. That's way the dimension time is set to 3. | |
| 857 | |
| 858 The first +/-45 degrees measurement starts at “20130620 22:00:00” (start | |
| 859 time of the first +45 measurement) and stops at “20130620 22:03:30” | |
| 860 (stop time of the fist -45 measurement). As a consequence, according to | |
| 861 the values of the global attributes RawData\_Start\_Date and | |
| 862 RawData\_Start\_Time\_UT we have to set: | |
| 863 | |
| 864 Raw\_Data\_Start\_Time[0]=0 (start of the first +45 measurement in | |
| 865 seconds since RawData\_Start\_Time\_UT) | |
| 866 | |
| 867 Raw\_Data\_Stop\_Time[0]=210 (stop of the first -45 measurement in | |
| 868 seconds since RawData\_Start\_Time\_UT) | |
| 869 | |
| 870 Following a similar procedure for the other 2 cycles we have: | |
| 871 | |
| 872 Raw\_Data\_Start\_Time[1]=300 (start of the second +45 measurement in | |
| 873 seconds since RawData\_Start\_Time\_UT) | |
| 874 | |
| 875 Raw\_Data\_Stop\_Time[1]=510 (stop of the second -45 measurement in | |
| 876 seconds since RawData\_Start\_Time\_UT) | |
| 877 | |
| 878 Raw\_Data\_Start\_Time[2]=600 (start of the third +45 measurement in | |
| 879 seconds since RawData\_Start\_Time\_UT) | |
| 880 | |
| 881 Raw\_Data\_Stop\_Time[2]=810 (stop of the third -45 measurement in | |
| 882 seconds since RawData\_Start\_Time\_UT) | |
| 883 | |
| 884 Moreover, according to the order of the channels in the channel\_ID | |
| 885 variable, the Raw\_Lidar\_Data array should be filled as it follows: | |
| 886 | |
| 887 Raw\_Lidar\_Data[0][0][points] → 1\ :sup:`st` measured transmitted | |
| 888 signal at +45 degrees | |
| 889 | |
| 890 Raw\_Lidar\_Data[0][1][points] → 1\ :sup:`st` measured reflected signal | |
| 891 at +45 degrees | |
| 892 | |
| 893 Raw\_Lidar\_Data[0][2][points] → 1\ :sup:`st` measured transmitted | |
| 894 signal at -45 degrees | |
| 895 | |
| 896 Raw\_Lidar\_Data[0][3][points] → 1\ :sup:`st` measured reflected signal | |
| 897 at -45 degrees | |
| 898 | |
| 899 Raw\_Lidar\_Data[1][0][points] → 2\ :sup:`nd` measured transmitted | |
| 900 signal at +45 degrees | |
| 901 | |
| 902 Raw\_Lidar\_Data[1][1][points] → 2\ :sup:`nd` measured reflected signal | |
| 903 at +45 degrees | |
| 904 | |
| 905 Raw\_Lidar\_Data[1][2][points] → 2\ :sup:`nd` measured transmitted | |
| 906 signal at -45 degrees | |
| 907 | |
| 908 Raw\_Lidar\_Data[1][3][points] → 2\ :sup:`nd` measured reflected signal | |
| 909 at -45 degrees | |
| 910 | |
| 911 Raw\_Lidar\_Data[2][0][points] → 3\ :sup:`rd` measured transmitted | |
| 912 signal at +45 degrees | |
| 913 | |
| 914 Raw\_Lidar\_Data[2][1][points] → 3\ :sup:`rd` measured reflected signal | |
| 915 at +45 degrees | |
| 916 | |
| 917 Raw\_Lidar\_Data[2][2][points] → 3\ :sup:`rd` measured transmitted | |
| 918 signal at -45 degrees | |
| 919 | |
| 920 Raw\_Lidar\_Data[2][3][points] → 3\ :sup:`rd` measured reflected signal | |
| 921 at -45 degrees | |
| 922 | |
| 923 Once this file has been created it needs to be submitted to the SCC and | |
| 924 linked to the configuration “depol\_calibration”. The result of the SCC | |
| 925 analysis on this file will be the calculation of the calibration | |
| 926 constant h\ :sup:`\*` that will be logged into the SCC database and can | |
| 927 be used to calibrate Raman/Elastic backscat ter products (see section | |
| 928 3.3). | |
| 929 | |
| 930 **Definition of “Raman/Elastic backscatter and linear depolarization ratio”** | |
| 931 ----------------------------------------------------------------------------- | |
| 932 | |
| 933 In order to calculate the *PLDR* we need to modify the polarization | |
| 934 related products linked to the “standard” measurement configurations | |
| 935 (the configuration called “nighttime” and/or “daytime” in table 3.2). | |
| 936 | |
| 937 Let's suppose we have defined the following products (defined already in | |
| 938 SCC v3.11): | |
| 939 | |
| 940 **Table 3.4:** Example of products configuration in SCC v3.11 | |
| 941 | |
| 942 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 943 | Product Name | Product ID | Product Type | nighttime | daytime | | |
| 944 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 945 | Raman backscatter | 1 | Raman backscatter | | | | |
| 946 | | | | | | | |
| 947 | 355nm | | | | | | |
| 948 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 949 | Extinction | 2 | Extinction | | | | |
| 950 | | | | | | | |
| 951 | 387nm | | | | | | |
| 952 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 953 | Raman backscatter | 3 | Raman backscatter | | | | |
| 954 | | | | | | | |
| 955 | 532nm | | | | | | |
| 956 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 957 | Extinction | 4 | Extinction | | | | |
| 958 | | | | | | | |
| 959 | 532nm | | | | | | |
| 960 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 961 | Elastic backscatter | 5 | Elastic backscatter | | | | |
| 962 | | | | | | | |
| 963 | 355nm | | | | | | |
| 964 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 965 | Elastic backscatter | 6 | Elastic backscatter | | | | |
| 966 | | | | | | | |
| 967 | 532nm | | | | | | |
| 968 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 969 | Elastic backscatter | 7 | Elastic backscatter | | | | |
| 970 | | | | | | | |
| 971 | 1064nm | | | | | | |
| 972 +-----------------------+--------------+-----------------------+-------------+-----------+ | |
| 973 | |
| 974 Product ID=1, 2, 4, 5, 7 do not need any modification as they do not | |
| 975 involve polarization channels. The only product that need to be modified | |
| 976 are the Product ID=3 and 6. To produce b532 files containing also *PLDR* | |
| 977 we need to modify the “nighttime” and “daytime” configurations to | |
| 978 include a product of type “Raman bakscatter and linear depolarization | |
| 979 ratio” or “Elastic bakscatter and linear depolarization ratio” | |
| 980 respectively. So the configuration reported in table 3.4 should be | |
| 981 changed to match what is included in table 3.5. | |
| 982 | |
| 983 **Table 3.5:** The same of table 3.4 but with new product types | |
| 984 introduced in SCC v4.0 | |
| 985 | |
| 986 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 987 | Product Name | Product ID | Product Type | nighttime | daytime | | |
| 988 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 989 | Raman backscatter | 1 | Raman backscatter | | | | |
| 990 | | | | | | | |
| 991 | 355nm | | | | | | |
| 992 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 993 | Extinction | 2 | Extinction | | | | |
| 994 | | | | | | | |
| 995 | 387nm | | | | | | |
| 996 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 997 | Raman backscatter | 10 | **Raman backscatter and linear depolarization ratio** | | | | |
| 998 | | | | | | | |
| 999 | 532nm | | | | | | |
| 1000 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 1001 | Extinction | 4 | Extinction | | | | |
| 1002 | | | | | | | |
| 1003 | 532nm | | | | | | |
| 1004 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 1005 | Elastic backscatter | 5 | Elastic backscatter | | | | |
| 1006 | | | | | | | |
| 1007 | 355nm | | | | | | |
| 1008 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 1009 | Elastic backscatter | 11 | **Elastic backscatter and linear depolarization ratio** | | | | |
| 1010 | | | | | | | |
| 1011 | 532nm | | | | | | |
| 1012 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 1013 | Elastic backscatter | 7 | Elastic backscatter | | | | |
| 1014 | | | | | | | |
| 1015 | 1064nm | | | | | | |
| 1016 +-----------------------+--------------+-----------------------------------------------------------+-------------+-----------+ | |
| 1017 | |
| 1018 As you can see in table 3.5, the old product IDs=3 and 6 (present in | |
| 1019 table 3.4) have been replaced with the new product ID=10 and 11 to | |
| 1020 guarantee the calculation of *PLDR*. | |
| 1021 | |
| 1022 It is important to set among the product options of the product ID=10 | |
| 1023 and 11 which calibration product we want to use for calibration (see | |
| 1024 section 3.2). This can be done using the SCC web interface setting the | |
| 1025 appropriate setting in the tab *Polarization calibration products* (see | |
| 1026 figure 3.4). According to the current example you should set here the | |
| 1027 calibration product defined in section 3.2. | |
| 1028 | |
| 1029 |image3| How to link a product to calibrate with a calibration product. | |
| 1030 | |
| 1031 **WARNING:** Please not that also *Raman/Elastic backscatter products* | |
| 1032 need to be linked to a calibration product because the calibration | |
| 1033 constant and the corresponding correction factor is needed to calculate | |
| 1034 the total signal out of the two polarization components even if the | |
| 1035 *PLDR* is not involved in the product calculation. | |
| 1036 | |
| 1037 .. |image0| image:: ./media/image1.png | |
| 1038 :width: 6.69514in | |
| 1039 :height: 2.40764in | |
| 1040 .. |image1| image:: ./media/image2.png | |
| 1041 :width: 6.69306in | |
| 1042 :height: 1.71458in | |
| 1043 .. |image2| image:: ./media/image3.png | |
| 1044 :width: 6.69306in | |
| 1045 :height: 1.77431in | |
| 1046 .. |image3| image:: ./media/image4.png | |
| 1047 :width: 6.69306in | |
| 1048 :height: 0.36389in |
