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docs/depolarization/depolarization.rst

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1 **Single Calculus Chain ** 1 1. Particle Linear Depolarization Ratio Implementation
2 2 ======================================================
3 **version: 4.0** 3
4 4 The most important improvement included in the SCC v4.0 is the implementation of a new optical product which is the particle linear depolarization ratio.
5 **date: Date (fixed)** 5
6 6 1.1 Background
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 -------------- 7 --------------
44 8
45 The calculation of the volume linear depolarization ratio profile 9 The calculation of the volume linear depolarization ratio profile (*VLDR*) and particle linear depolarization ratio profile (*PLDR*) needs two different steps:
46 (*VLDR*) and particle linear depolarization ratio profile (*PLDR*) needs 10
47 two different steps: 11 #. the calibration of the polarization sensitive lidar channels;
48 12 #. the calculation of the *VLDR* or *PLDR* itself.
49 1. the calibration of the polarization sensitive lidar channels; 13
50 14 The SCC allows the user to make both the above points. In particular the calibration step is made by a completely new module called **scc\_calibrator** which computes the *apparent calibration factor* :math:`\beta^*` out of the pre-processed data provided by the standard **ELPP** (Earlinet Lidar Pre-Processor) module and it records it in the SCC database (SCC\_DB). Once logged into the SCC\_DB this factor can be used whenever it is necessary.
51 2. the calculation of the *VLDR* or *PLDR* itself. 15
52 16 The raw lidar calibration measurements should be put in a NetCDF file which has the same structure as the “standard” raw SCC NetCDF input file (for more details see sections 2 and 3.2).
53 The SCC allows the user to make both the above points. In particular the 17
54 calibration step is made by a completely new module called 18 New signal types have been introduced to take into account special channel configurations used for calibration purposes.
55 **scc\_calibrator** which computes the *apparent calibration factor* 19
56 h\ :sup:`\*` out of the pre-processed data provided by the standard 20 Moreover new product types for both calibration and *PLDR* calculation have been defined. As, in principle, it is possible to calculate the *PLDR* only when the aerosol backscatter coefficient profile is available the following new products have been defined:
57 **ELPP** (Earlinet Lidar Pre-Processor) module and it records it in the 21
58 SCC database (SCC\_DB). Once logged into the SCC\_DB this factor can be 22 #. *Linear polarization calibration (factor* h) *(product\_type\_id=6);*
59 used whenever it is necessary. 23 #. *Raman backscatter and linear depolarization ratio
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);* 24 (product\_type\_id=7);*
77 25 #. *Elastic backscatter and linear depolarization ratio
78 3. *Elastic backscatter and linear depolarization ratio
79 (product\_type\_id=8).* 26 (product\_type\_id=8).*
80 27
81 The first product in the above list is used only for calibration while 28 The first product in the above list is used only for calibration while the other two are used for the calculation of *PLDR*. Basically, in most of the cases, the products 2 and 3 are equivalent to the corresponding backscatter product types with the exception that also the following new variables are available:
82 the other two are used for the calculation of *PLDR*. Basically, in most 29
83 of the cases, the products 2 and 3 are equivalent to the corresponding 30 .. code-block:: python
84 backscatter product types with the exception that also the following new 31
85 variables are available: 32 double VolumeDepol(Length) ;
86 33 double ErrorVolumeDepol(Length) ;
87 double VolumeDepol(Length) ; 34 ErrorVolumeDepol:long\_name = "absolute error of VolumeDepol" ;
88 35 double ParticleDepol(Length) ;
89 double ErrorVolumeDepol(Length) ; 36 double ErrorParticleDepol(Length) ;
90 37 ErrorParticleDepol:long\_name = "absolute error of ParticleDepol" ;
91 ErrorVolumeDepol:long\_name = "absolute error of VolumeDepol" ; 38
92 39 1.2 Polarization calibration
93 double ParticleDepol(Length) ;
94
95 double ErrorParticleDepol(Length) ;
96
97 ErrorParticleDepol:long\_name = "absolute error of ParticleDepol" ;
98
99 **Polarization calibration**
100 ---------------------------- 40 ----------------------------
101 41
102 An important point is the definition of reliable *PLDR* calibration 42 An important point is the definition of reliable *PLDR* calibration procedures. Within EARLINET the following calibration procedures are currently used:
103 procedures. Within EARLINET the following calibration procedures are 43
104 currently used: 44 a) Rayleigh calibration;
105 45 b) +45 calibration method, or D90 calibration method (made by +45 and -45 measurements);
106 a) Rayleigh calibration; 46 c) 3 signals (total, cross and parallel).
107 47
108 b) +45 calibration method, or D90 calibration method (made by +45 and 48 It is well known that method a) could produce easily large errors on *PLDR* which cannot be controlled. For this reason only the methods b) and c) can be used to provide reliable polarization calibrations and so only those methods will be implemented in the SCC.
109 -45 measurements); 49
110 50 For what it concerns the method c) it, basically, requires to solve the equation:
111 c) 3 signals (total, cross and parallel). 51
112 52 .. math::
113 It is well known that method a) could produce easily large errors on 53 \alpha_s P_s + \alpha_p P_p = P
114 *PLDR* which cannot be controlled. For this reason only the methods b) 54
115 and c) can be used to provide reliable polarization calibrations and so 55 in two different of atmospheric layers with considerably different *VLDR*. So to calibrate in this way the implementation of automatic layer identification in the SCC is required. As at moment this feature is not yet available within the SCC *ONLY* the method b) is considered.
116 only those methods will be implemented in the SCC. 56
117 57 1.3 SCC procedure to calculate the PLDRP
118 For what it concerns the method c) it, basically, requires to solve the 58 ----------------------------------------
119 equation: 59
120 60 According to what mentioned before the SCC calculates the *PLDR* through the following steps:
121 in two different of atmospheric layers with considerably different 61
122 *VLDR*. So to calibrate in this way the implementation of automatic 62 #. The user needs to create a new system configuration in the SCC\_DB including only lidar channels used for the calibration. One (or more) *Linear polarization calibration (product\_type\_id=6)* product should be associated to this new configuration (see section 3.2 for more details);
123 layer identification in the SCC is required. As at moment this feature 63
124 is not yet available within the SCC *ONLY* the method b) is considered. 64 #. This new system configuration should contain only the polarization channels in the configuration used for the calibration (for example rotated in the polarization plane of +45 degrees). A channel in calibration measurement configuration should have a *DIFFERENT* channel ID from the channel ID corresponding to the same channel in standard measurement configuration. For example, if a system has two polarization channels which in standard measurement configuration correspond to the channel ID=1 and 2 respectively, the same physical channels under calibration measurement configuration should correspond to different channel IDs (let's say ID=3 and 4 for the +45 degrees polarization rotated channels and ID=5 and 6 for the -45 degrees polarization rotated ones in case D90 calibration method is used). Moreover, the polarization channels should be labeled correctly using the new signal types available (*+45elPT, +45elPR, -45elPT, -45elPR, +45elPTnr, +45elPTfr, +45elPRnr, +45elPRfr, -45elPTnr, -45elPTfr, -45elPRnr, -45elPRfr).* For more details see section 3.2;
125 65
126 SCC procedure to calculate the PLDRP 66 #. In SCC v4.0 the polarization channels are *NOT* labeled on the base of their polarization state (as it was done in the SCC v3.11) but *ALWAYS* as transmitted and reflected channels. So the channels that in SCC v3.11 were labeled as *elCP, elCPnr, elCPfr, elPP, elPPnr elPPfr* will be labeled in SCC v4.0 as *elPR, elPRnr elPRfr elPT, elPTnr elPTfr* where the letter *T* stands from transmitted and the letter *R* for reflected.
127 ------------------------------------ 67
128 68 :WARNING: In switching from the SCC v3.11 to SCC v4.0 the following modifications have been made on *ALL* channels of *ALL* registered configurations:
129 According to what mentioned before the SCC calculates the *PLDR* through 69 *elPP→elPR*
130 the following steps: 70
131 71 *elCP→elPT*
132 1. The user needs to create a new system configuration in the SCC\_DB 72
133 including only lidar channels used for the calibration. One (or more) 73 *elPPnr→elPRnr*
134 *Linear polarization calibration (product\_type\_id=6)* product 74
135 should be associated to this new configuration (see section 3.2 for 75 *elPPfr→ elPRfr*
136 more details); 76
137 77 *elCPnr→ elPTnr*
138 2. This new system configuration should contain only the polarization 78
139 channels in the configuration used for the calibration (for example 79 *elCPfr→ elPTfr*
140 rotated in the polarization plane of +45 degrees). A channel in 80
141 calibration measurement configuration should have a *DIFFERENT* 81 Please be sure these modifications reflect to your actual lidar setup(cross channels are transmitted and parallel channels are reflected);
142 channel ID from the channel ID corresponding to the same channel in 82
143 standard measurement configuration. For example, if a system has two 83 4. The user needs to submit a file (same format as raw SCC input file) containing the raw data for the lidar channels defined at the point 1 (see section 3.2 for more details);
144 polarization channels which in standard measurement configuration 84 #. The file at point 2 is pre-processed by **ELPP** module which applies the standard pre-processing procedures applied to “standard” lidar data;
145 correspond to the channel ID=1 and 2 respectively, the same physical 85 #. The pre-processed files are then processed by the new modules **scc\_calibrator** which calculates :math:`\eta^*` *the apparent calibration factor* and logs it into the SCC\_DB;
146 channels under calibration measurement configuration should 86 #. The user needs to create a new system configuration in the SCC\_DB (which should be different from the one used for the calibration) and associate it the new product *Raman backscatter and linear depolarization ratio product\_type\_id=7)* or *Elastic backscatter and linear depolarization ratio (product\_type\_id=8).* Alternatively the calculation of those products can be added to an already existing lidar configuration as long as it is different from the calibration one;
147 correspond to different channel IDs (let's say ID=3 and 4 for the +45 87 #. The product defined at point 5 should be linked to the product containing the polarization calibration (defined at point 1) in a way that the *apparent calibration factor* can be selected from the SCC\_DB (see section 3.3 and in particular figure 3.4);
148 degrees polarization rotated channels and ID=5 and 6 for the -45 88 #. The user needs to submit another SCC raw data file containing the “standard” measurements;
149 degrees polarization rotated ones in case D90 calibration method is 89 #. Finally **ELPP** and **ELDA** will produce a b-file containing backscatter coefficient profile and *PLDR*. In particular this calculation is made in two different steps: from the pre-processed lidar polarization signals, and taking into account the *apparent calibration factor* and the *calibration factor correction K* (defined as option of *Linear polarization calibration* product\ *)* written into the SCC\_DB, an “apparent” *VLDR* :math:`\delta^*` is calculated. Even if :math:`\delta^*` is a calibrated quantity it can be still affected by possible systematic errors due to not perfect optics or alignment of the system;
150 used). Moreover, the polarization channels should be labeled 90
151 correctly using the new signal types available (*+45elPT, +45elPR, 91 #. To take into account these errors a corrected *VLDR* (:math:`\delta`) is calculated using the *polarization cross-talk correction parameters* *G* and *H* calculated on the base of Müller matrix formalism. These cross-talk correction parameters (*G* and *H*) are stored in the SCC\_DB for each lidar channels (see section 3.1 in particular figure 3.2). Finally the *PLDR* is calculated using the backscatter coefficient profile and the molecular LDRP calculated by ELPP considering the center wavelength and bandwidth of the channels interference filter.
152 -45elPT, -45elPR, +45elPTnr, +45elPTfr, +45elPRnr, +45elPRfr, 92
153 -45elPTnr, -45elPTfr, -45elPRnr, -45elPRfr).* For more details see 93 The *apparent calibration factor* :math:`\eta^*` is calculated by the **scc\_calibrator** module as the geometrical mean of the ratio of the +/-45 degrees reflected to the +/- 45 degrees transmitted signals within an altitude calibration range defined by the users in the raw data input files.
154 section 3.2; 94
155 95 In case of +45 calibration method :math:`\eta^*` is calculated by:
156 3. In SCC v4.0 the polarization channels are *NOT* labeled on the base 96
157 of their polarization state (as it was done in the SCC v3.11) but 97 .. math::
158 *ALWAYS* as transmitted and reflected channels. So the channels that 98 \eta^* = \frac{I_R}{I_T}(+45)
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 99
243 While in case of D90 calibration method: 100 While in case of D90 calibration method:
244 101
245 (1.2) 102 .. math::
103 \eta^* = \sqrt{\frac{I_R}{I_T}(+45) \frac{I_R}{I_T}(-45)}
246 104
247 **ELDA** module calculates the “apparent” *VLDR*: 105 **ELDA** module calculates the “apparent” *VLDR*:
248 106
249 (1.3) 107 .. math::
108 \delta^* = \frac{K}{\eta^*} \cdot \frac{I_R}{I_T}
250 109
251 the *VLDR* 110 the *VLDR*
252 111
253 (1.4) 112 .. math::
113 \delta = \frac{\delta^*(G_T + H_T)-(G_R + H_R)}{(G_R - H_R) - \delta^*(G_T - H_T)}
254 114
255 and the *PLDR* 115 and the *PLDR*
256 116
257 (1.5) 117 .. math::
118 \delta_{\alpha} = \frac{(1 + \delta_m)\delta R - (1 + \delta)\delta_m}{(1 + \delta_m)R - (1 + \delta)}
258 119
259 where: 120 where:
260 121
261 - h\ :sup:`\*` is the *apparent calibration factor* calculated by 122 - :math:`\eta^*` is the *apparent calibration factor* calculated by **scc\_calibrator**
262 **scc\_calibrator** 123
263 124 - *K* is the *calibration factor correction* defined as polarization product option
264 - *K* is the *calibration factor correction* defined as polarization 125
265 product option 126 - :math:`I_T` and :math:`I_R` are the transmitted and the reflected signals in the polarization detection set-up
266 127
267 - *I\ :sub:`T`* and I\ *:sub:`R`* are the transmitted and the reflected 128 - :math:`G_{T,R}` and :math:`H_{T,R}` are *polarization cross-talk correction parameters* for the transmitted and reflected signals used to correct for systematic errors. Both these factors are defined in the SCC\_DB for each lidar channel.
268 signals in the polarization detection set-up 129
269 130 - :math:`\delta_m` is the molecular linear depolarization ratio calculated by ELPP
270 - *G\ :sub:`T,R`* and *H\ :sub:`T,R`* are *polarization cross-talk 131
271 correction parameters* for the transmitted and reflected signals used 132 - *R* is the backscatter ratio
272 to correct for systematic errors. Both these factors are defined in 133
273 the SCC\_DB for each lidar channel. 134 Please note once again that the polarization channels are described in terms of transmitted and reflected signals. This means that according to different lidar instrumental configurations, the transmitted or the reflected channel can contain total, perpendicular or parallel polarized signals.
274 135
275 - *d\ :sub:`m`* is the molecular linear depolarization ratio calculated 136 In order to retrieve the backscatter profile the total signal must be obtained combining the transmitted and reflected polarized signals. The following formula is used:
276 by ELPP 137
277 138 .. math::
278 - *R* is the backscatter ratio 139 I_{total} \propto \frac{\eta^*}{K}H_R I_T - H_T I_R
279 140
280 Please note once again that the polarization channels are described in 141 The formulas above are general and can be adapted to all possible polarization lidar configurations selecting the right polarization cross-talk correction parameters (see Table 1.1).
281 terms of transmitted and reflected signals. This means that according to 142
282 different lidar instrumental configurations, the transmitted or the 143 Let's suppose, for example, we have the perpendicular polarized lidar signal on the transmitted channel and the parallel polarized on reflected channel. For an ideal system (no diattenuation and cross-talk) we have:
283 reflected channel can contain total, perpendicular or parallel polarized 144
284 signals. 145 .. math::
285 146 G_T=1 , \qquad H_T=-1, \qquad G_R=1, \qquad H_R=1
286 In order to retrieve the backscatter profile the total signal must be 147
287 obtained combining the transmitted and reflected polarized signals. The 148 If, on the other hands, we have the perpendicular polarized lidar signal on reflected channel and the total polarized on the transmitted for and ideal system we have:
288 following formula is used: 149
289 150 .. math::
290 (1.6) 151 G_T=1 , \qquad H_T=0, \qquad G_R=1, \qquad H_R=-1
291 152
292 The formulas above are general and can be adapted to all possible 153
293 polarization lidar configurations selecting the right polarization 154 **Table 1.1:** Polarization cross-talk correction parameters for ideal systems
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
307 155
308 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 156 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
309 | Laser polarization | Detected in lidar channel | 157 | Laser polarization | Detected in lidar channel |
310 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 158 + +-----------------------------+-----------------+-----------------+-----------------+
311 | | Transmitted | Reflected | 159 | | Transmitted | Reflected |
312 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 160 + +-----------------------------+-----------------+-----------------+-----------------+
313 | | *G\ :sub:`T`* | *H\ :sub:`T`* | *G\ :sub:`R`* | *H\ :sub:`R`* | 161 | | :math:`G_T` | :math:`H_T` | :math:`G_R` | :math:`H_R` |
314 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 162 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
315 | total | 1 | 0 | 1 | 0 | 163 | total | 1 | 0 | 1 | 0 |
316 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 164 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
317 | parallel | 1 | 1 | 1 | 1 | 165 | parallel | 1 | 1 | 1 | 1 |
318 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 166 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
319 | cross | 1 | -1 | 1 | -1 | 167 | cross | 1 | -1 | 1 | -1 |
320 +----------------------+-----------------------------+-----------------+-----------------+-----------------+ 168 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
321 169
322 The *apparent calibration factor* (h:sup:`\*`), *the calibration factor 170 The *apparent calibration factor (:math:`\eta^*`), *the calibration factor correction* (*K*) and the *polarization cross-talk correction parameters* are stored by **ELPP** module in the intermediate NetCDF files using the following variables:
323 correction* (*K*) and the *polarization cross-talk correction 171
324 parameters* are stored by **ELPP** module in the intermediate NetCDF 172 testing the inline code :code:`test`
325 files using the following variables: 173
326 174 - :code:`Polarization_Channel_Gain_Factor` (*apparent calibration factor* - :math:`\eta^*` )
327 - *Polarization\_Channel\_Gain\_Factor (apparent calibration factor* – 175 - :code:`Polarization_Channel_Gain_Factor_Correction` (*calib. factor corr.* – *K*)
328 h\ :sup:`\*`) 176 - :code:`G_T`
329 177 - :code:`H_T`
330 - *Polarization\_Channel\_Gain\_Factor\_Correction (calib. factor 178 - :code:`G_R`
331 corr.* – *K*) 179 - :code:`H_R`
332 180
333 - *G\_T* 181 Finally new usecases have been defined to take into account all the possible lidar configurations. The details on that are provided as a separate file.
334 182
335 - *H\_T* 183 2. Changes of the SCC input format
336 184 ==================================
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 ===============================
347 185
348 The following minor changes have been applied to raw SCC data format: 186 The following minor changes have been applied to raw SCC data format:
349 187
350 1. The optional variable *ID\_Range* has been *REMOVED*; 188 #. The optional variable *ID\_Range* has been *REMOVED*;
351 189 #. The *OPTIONAL* variable :code:`int Signal\_Type(channels)` has been added. The possible values are the same available in the SCC\_DB:
352 2. The *OPTIONAL* variable *int Signal\_Type(channels)* has been added. 190
353 The possible values are the same available in the SCC\_DB: 191 :code:`0` :math:`\rightarrow` :code:`elT`
354 192
355 0 *→* elT 193 :code:`1` :math:`\rightarrow` :code:`elTnr`
356 194
357 1 *→* elTnr 195 :code:`2` :math:`\rightarrow` :code:`elTfr`
358 196
359 2 *→* elTfr 197 :code:`3` :math:`\rightarrow` :code:`vrRN2`
360 198
361 3 *→* vrRN2 199 :code:`4` :math:`\rightarrow` :code:`vrRN2nr`
362 200
363 4 *→* vrRN2nr 201 :code:`5` :math:`\rightarrow` :code:`vrRN2fr`
364 202
365 5 *→* vrRN2fr 203 :code:`6` :math:`\rightarrow` :code:`elPR`
366 204
367 6 *→* elPR 205 :code:`7` :math:`\rightarrow` :code:`elPT`
368 206
369 7 *→* elPT 207 :code:`8` :math:`\rightarrow` :code:`pRRlow`
370 208
371 8 *→* pRRlow 209 :code:`9` :math:`\rightarrow` :code:`pRRhigh`
372 210
373 9 *→* pRRhigh 211 :code:`10` :math:`\rightarrow` :code:`elPRnr`
374 212
375 10 *→* elPRnr 213 :code:`11` :math:`\rightarrow` :code:`elPRfr`
376 214
377 11 *→* elPRfr 215 :code:`12` :math:`\rightarrow` :code:`elPTnr`
378 216
379 12 *→* elPTnr 217 :code:`13` :math:`\rightarrow` :code:`elPTfr`
380 218
381 13 *→* elPTfr 219 :code:`14` :math:`\rightarrow` :code:`vrRH2O`
382 220
383 14 *→* vrRH2O 221 :code:`15` :math:`\rightarrow` :code:`pRRhighnr`
384 222
385 15 *→* pRRhighnr 223 :code:`16` :math:`\rightarrow` :code:`pRRhighfr`
386 224
387 16 *→* pRRhighfr 225 :code:`17` :math:`\rightarrow` :code:`pRRlownr`
388 226
389 17 *→* pRRlownr 227 :code:`18` :math:`\rightarrow` :code:`pRRlowfr`
390 228
391 18 *→* pRRlowfr 229 :code:`19` :math:`\rightarrow` :code:`vrRH2Onr`
392 230
393 19 *→* vrRH2Onr 231 :code:`20` :math:`\rightarrow` :code:`vrRH2Ofr`
394 232
395 20 *→* vrRH2Ofr 233 :code:`21` :math:`\rightarrow` :code:`elTunr`
396 234
397 21 *→* elTunr 235 :code:`22` :math:`\rightarrow` :code:`+45elPT`
398 236
399 *22 → +45elPT* 237 :code:`23` :math:`\rightarrow` :code:`+45elPR`
400 238
401 *23 → +45elPR* 239 :code:`24` :math:`\rightarrow` :code:`-45elPT`
402 240
403 *24 → -45elPT* 241 :code:`25` :math:`\rightarrow` :code:`-45elPR`
404 242
405 *25 → -45elPR* 243 :code:`26` :math:`\rightarrow` :code:`+45elPTnr`
406 244
407 *26 → +45elPTnr* 245 :code:`27` :math:`\rightarrow` :code:`+45elPTfr`
408 246
409 *27 → +45elPTfr* 247 :code:`28` :math:`\rightarrow` :code:`+45elPRnr`
410 248
411 *28 → +45elPRnr* 249 :code:`29` :math:`\rightarrow` :code:`+45elPRfr`
412 250
413 *29 → +45elPRfr* 251 :code:`30` :math:`\rightarrow` :code:`-45elPTnr`
414 252
415 *30 → -45elPTnr* 253 :code:`31` :math:`\rightarrow` :code:`-45elPTfr`
416 254
417 *31 → -45elPTfr* 255 :code:`32` :math:`\rightarrow` :code:`-45elPRnr`
418 256
419 *32 → -45elPRnr* 257 :code:`33` :math:`\rightarrow` :code:`-45elPRfr`
420 258
421 *33 → -45elPRfr* 259 :WARNING: It this variable is found in the SCC input file the corresponding settings in the SCC database will be *overwritten*. Unless you don't have any valid reason to overwrite the database value this variable should not be used.
422 260
423 **WARNING:** It this variable is found in the SCC input file the 261 3. The variables:
424 corresponding settings in the SCC database will be *overwritten*. Unless 262
425 you don't have any valid reason to overwrite the database value this 263 .. code-block:: python
426 variable should not be used. 264
427 265 double Pol\_Calib\_Range\_Min(channels)
428 1. The variables: 266 double Pol\_Calib\_Range\_Max(channels)
429 267
430 *double Pol\_Calib\_Range\_Min(channels)* 268 have been added. Both these variable are *MANDATORY* for any calibration raw dataset. These variable should be included only the polarization calibration measurements and should specify the altitude range (meters) in which the polarization calibration should be made. For more details see section 3.3;
431 269
432 *double Pol\_Calib\_Range\_Max(channels) * 270 4. The variable :code:`Depolarization_Factor` has been *REMOVED*.
433 271
434 have been added. Both these variable are *mandatory* for any calibration 272 The SCC v3.11 used this variable to get polarization calibration factor for the calculation of the total signal out of cross and parallels ones. As the SCC v4.0 is able to calculate the same parameter by itself, the use of this variable is *NOT* possible anymore. The recommended way to get a valid and quality assured depolarization calibration factor is to submit to the SCC v4.0 a polarization calibration dataset and let the SCC to calculate such factor.
435 raw dataset. 273
436 274 To make this change more smooth and to provide the users with the possibility to continue to analyze their data with the SCC v4.0 even if a calibration dataset has not been submitted yet, it will be possible for a *LIMITED* period of time to submit the calibration constant via the SCC web interface. The SCC will keep track of the used calibration method (automatic or manual).
437 These variable should be included only the polarization calibration 275
438 measurements and should specify the altitude range (meters) in which the 276 :WARNING: After this transition period *ONLY* automatic calibration will be allowed!
439 polarization calibration should be made. For more details see section 277
440 3.3; 278 5. The new *OPTIONAL* variable:
441 279
442 1. The variable *Depolarization\_Factor* has been *removed*. 280 :code:`string channel\_string\_ID(channels)`
443 281
444 The SCC v3.11 used this variable to get polarization calibration factor 282 has been introduced.
445 for the calculation of the total signal out of cross and parallels ones. 283
446 As the SCC v4.0 is able to calculate the same parameter by itself, the 284 Starting from SCC v4.0 the lidar channel can be identified not only by using integers (as it happened until SCC v3.11) but also by using strings.
447 use of this variable is *NOT* possible anymore. The recommended way to 285
448 get a valid and quality assured depolarization calibration factor is to 286 The procedure implemented in the SCC v4.0 to recognize the lidar channel within the raw lidar data is fully backward compatible (old format files are accepted as they are by SCC v4.0).
449 submit to the SCC v4.0 a polarization calibration dataset and let the 287
450 SCC to calculate such factor. 288 :WARNING: Please note that the definition of the new string variable requires netCDF-4 format! The type *string* is not supported in netCDF-3 format!
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!
479 289
480 Real Example 290 Real Example
481 ============ 291 ============
482 292
483 This section describes all the practical steps the users need to follow 293 This section describes all the practical steps the users need to follow

EARLINET Repository: SCC Documentation

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