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GLA11 Records: Release 33

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GLA11 contains the layer-by-layer optical results of the GLAS 532 nm atmospheric vertical profiles, i.e., the optical depth and multiple scattering factor separated into cloud and aerosol components. Polar stratospheric clouds are part of the aerosol category. To obtain the total column optical depth, you should add the aerosol and cloud components. For every atmospheric layer detected by 532 nm, a multiple scattering flag reflects the current multiple scattering condition.

GLA11 contains top and bottom heights of all the layers that were optically processed, separated into cloud and aerosol. All cloud products, including optical depth, multiple scattering factor, and layer tops and bottoms, are reported at a 1 sec sampling rate. These are the same layers as reported in GLA09. The aerosol products, output to GLA08, are reported at a 4 sec sampling rate.

The "ground detection" parameter refers to the height where the lidar sensed the ground. If the ground was not sensed, this parameter is set to "invalid." This parameter is useful for determining whether the last layer bottom sensed was a true bottom or if it marks the time when the lidar signal was extinguished. All layer locations are referenced from the geoid, and all extinction profiles were corrected for multiple scattering. The multiple scattering correction factor is stored in GLA11. Each GLA11 record is 4 sec long and contains one group of aerosol products and four groups of cloud products (one for each second). The time stamp refers to the J2000 time of the first shot of the record. J2000 time refers to the number of seconds since 01 January 2000 at 12:00 UTC.

The 532 nm cloud layer data are stored as 1 sec average values, and the 532 nm aerosol layer data are stored as 4 sec average values. The optical depth and multiple scattering factor values are recorded once per layer. There are up to 10 cloud layers in each cloud profile and up to nine aerosol layers in each aerosol profile; however, for the optical depth product, the nine layers are separated into eight elevated and one PBL height. Active layers are not necessarily grouped toward the front of the array sequence. For aerosols, the top three layer positions are reserved for layers above 20 km.

Optical depths for each layer have an associated composite flag variable that represents conditions in that layer. The composite flag is made up of two main components: a layer quality flag and a layer usage flag. In all cases, the quality flag is a categorized value of the percent error calculation. The usage flag designates layer type category. The "cloud multiple scattering warning flag" is a measure of multiple scattering intensity and is based on the total column optical depth. One value is calculated for each 1 sec profile.


Follow the links in the table below to the GLAS Atmosphere Data Dictionary for details of each record, including units and scaling factors. The GLAS science team created this dictionary. Units and scaling factors with a "d" indicate double-precision constants; for example, a value of "1.0d5" is equivalent to 100,000. The variable "pe/bin" represents photo electrons per bin.

The following codes are used to denote data types throughout the remainder of this document.

i1b: 1-byte integer
i2b: 2-byte (short) integer
i4b: 4-byte (long) integer
r4b: 4-byte real
r8b: 8-byte real

Values in parentheses indicate the record size, for example:

i2b (39): 39 records of 2-byte integers
i1b (48,40): 48-record x 40-record array of 1-byte integers

Nearly all integers are signed. Exceptions are noted in the following record table.


Name Short Description Byte Offset Data Type Total Bytes
i_rec_ndx GLAS record index 0 i4b 4
i_UTCTime Transmit time of first shot in frame in J2000 (referenced from noon on 01 January 2000) 4 i4b (2) 8
i_beam_coelev Co-elevation 12 i4b (4) 16
i_beam_azimuth Azimuth 28 i4b (4) 16
i_pad_angle PAD angle 44 i4b (4) 16
i_spare0 Spares 60 i1b (40) 40
i_AttFlg1 Attitude flag 100 i2b (4) 8
i_lat Profile location, latitude 108 i4b (4) 16
i_lon Profile location, longitude 124 i4b (4) 16
i_OrbFlg Orbit flag 140 i1b (2,4) 8
i_surfType Region type 148 i1b (4) 4
i_LidarQF Lidar frame quality flag 152 i2b (4) 8
i_cld1_od Cloud optical depth 160 i2b (10,4) 80
i_aer4_od Aerosol optical depth 240 i2b (8) 16
i_pbl4_od PBL optical depth 256 i2b 2
i_aer4_msf Aerosol multiple scattering factor 258 i2b (9) 18
i_cld1_msf Cloud multiple scattering factor 276 i2b (10,4) 80
i_cld1_bot Medium resolution cloud bottom 356 i2b (10,4) 80
i_cld1_top Medium resolution cloud top 436 i2b (10,4) 80
i_cld1_grd_det Medium resolution ground detection 516 i2b (4) 8
i_aer4_bot Low-resolution aerosol layer bottom 524 i2b (8) 16
i_aer4_top Low-resolution aerosol layer top 540 i2b (8) 16
i_aer4_ht Low-resolution PBL height 556 i2b 2
i_aer4_grd_det Low-resolution ground detection 558 i2b 2
i_erd Estimated range delay 560 i2b (4) 8
i_pse Particle size estimate 568 i2b (4) 8
i_cld1_mswf Cloud multiple scattering warning flag 576 i1b (2) 2
i_cld1_flag Cloud optical depth flag 578 i1b (40) 40
i_aer4_flag Aerosol optical depth flag 618 i1b (8) 8
i_pbl4_flag PBL optical depth flag 626 i1b 1
i_AttFlg3 Attitude flag 3 627 i1b 1
i_timecorflg Time correction flag 628 i2b 2
i_rdu Range delay uncertainty 630 i2b (4) 8
i_spare2 Spares 638 i1b (2) 2
i_SolarAngle Solar angle 640 i4b (4) 16
i_MRg_cldtop_temp Medium resolution 532 nm cloud top temperature 656 i2b (10, 4) 80
i_MRg_cldtop_pres Medium resolution 532 nm cloud top pressure 736 i2b (10, 4) 80
i_MRg_cldtop_relh Medium resolution 532 nm cloud top relative humidity 816 i2b (10, 4) 80
i_MRg_cldbot_temp Medium resolution 532 nm cloud bottom temperature 896 i2b (10, 4) 80
i_MRg_cldbot_pres Medium resolution 532 nm cloud bottom pressure 976 i2b (10, 4) 80
i_MRg_cldbot_relh Medium resolution 532 nm cloud bottom relative humidity 1056 i2b (10, 4) 80
i_Aer_top_temp Aerosol layers temperature at top of layer at 532 nm 1136 i2b (9) 18
i_Aer_top_pres Aerosol layers pressure at top of layer at 532 nm 1154 i2b (9) 18
i_Aer_top_relh Aerosol layers relative humidity at top of layer at 532 nm 1172 i2b (9) 18
i_Aer_bot_temp Aerosol layers temperature at bottom of layer at 532 nm 1190 i2b (9) 18
i_Aer_bot_pres Aerosol layers pressure at bottom of layer at 532 nm 1208 i2b (9) 18
i_Aer_bot_relh Aerosol layers relative humidity at bottom of layer at 532 nm 1226 i2b (9) 18
i_Aer_ir_top Elevation of top of aerosol layers detected in 1064 nm 1244 i2b (2) 4
i_Aer_ir_bot Elevation of bottom of aerosol layers detected in 1064 nm 1248 i2b (2) 4
i_Aer_ir_top_temp Temperature of top of aerosol layers detected in 1064 nm 1252 i2b (2) 4
i_Aer_ir_top_pres Pressure of top of aerosol layers detected in 1064 nm 1256 i2b (2) 4
i_Aer_ir_top_relh Relative Humidity of top of aerosol layers detected in 1064 nm 1260 i2b (2) 4
i_Aer_ir_bot_temp Temperature of bottom of aerosol layers detected in 1064 nm 1264 i2b (2) 4
i_Aer_ir_bot_pres Pressure of bottom of aerosol layers detected in 1064 nm 1268 i2b (2) 4
i_Aer_ir_bot_relh Relative humidity of bottom of aerosol layers detected in 1064 nm 1272 i2b (2) 4
i_MRir_cld_top Elevation of top of cloud layers detected in 1064 nm at medium resolution 1276 i2b (10, 4) 80
i_MRir_cld_bot Elevation of bottom of cloud layers detected in 1064 nm at medium resolution 1356 i2b (10, 4) 80
i_MRir_cldtop_temp Temperature of top of cloud layers detected in 1064 nm at medium resolution 1436 i2b (10, 4) 80
i_MRir_cldtop_pres Pressure of top of cloud layers detected in 1064 nm at medium resolution 1516 i2b (10, 4) 80
i_MRir_cldtop_relh Relative humidity of top of cloud layers in 1064 nm at medium resolution 1596 i2b (10, 4) 80
i_MRir_cldbot_temp Temperature of bottom of cloud layers detected in 1064 nm at medium resolution 1676 i2b (10, 4) 80
i_MRir_cldbot_pres Pressure of bottom of cloud layers detected in 1064 nm at medium resolution 1756 i2b (10, 4) 80
i_MRir_cldbot_relh Relative humidity of bottom of cloud layers detected in 1064 nm at medium resolution 1836 i2b (10, 4) 80
i_MRir_QAflag Medium resolution 1064 nm cloud layer QA flag 1916 i1b (40) 40
i_Aer_PBL_LR_temp Temperature of low resolution planetary boundary layer top at 532 nm 1956 i2b 2
i_Aer_PBL_LR_pres Pressure of low resolution planetary boundary layer top at 532 nm 1958 i2b 2
i_Aer_PBL_LR_relh Relative humidity of low resolution planetary boundary layer top at 532 nm 1960 i2b 2
i_Surface_temp Surface temperature 1962 i2b (4) 8
i_Surface_pres Surface pressure 1970 i2b (4) 8
i_Surface_relh Surface relative humidity 1978 i2b (4) 8
i_Surface_wind Surface wind speed 1986 i2b (4) 8
i_Surface_wdir Surface wind direction azimuth from north 1994 i2b (4) 8
i_Aer_ir_OD Aerosol optical depth at 1064 nm 2002 i2b (2) 4
i_cld_ir_OD Cloud optical depth at 1064 nm 2006 i2b (10, 4) 80
i_spare6 Spare 6 2086 i1b (202) 202
i_reflct_1064od_40hz_cor 40 Hz 1064 nm total column optical depth 2288 i2b (40,4) 320
i_reflct_1064msf_40hz 40 Hz 1064 nm multiple scattering correction factor 2608 i1b (160) 160
i_reflct_1064od_1hz_cor 1 Hz 1064 nm total column optical depth 2768 i2b (4) 8
i_reflct_1064msf_1hz 1 Hz 1064 nm multiple scattering correction factor 2776 i1b (4) 4
i_reflct_pristine_1hz 1064 nm modeled surface reflectance 2780 i2b (4) 8
i_aod_4s Total column Aerosol Optical Depth (AOD) 2788 i2b 2
i_aod_flg_4s AOD use flag 2790 i1b 1
i_spare3 Spares 2791 i1b 1
i_bs_erd Blowing snow range delay 2792 i2b (4) 8
i_bs_conf Blowing snow confidence 2800 i1b (4) 4
i_aer4_sval1 Aerosol true S Values from table 2804 i2b (9) 18
i_aer4_sval_ratio 532/1064 aerosol S ratio 2822 i2b (9) 18
i_aer4_aod_ratio 532/1064 aerosol optical depth ratio 2840 i2b (9) 18
i_aer4_sval_uf Aerosol true S Values use flag 2858 i1b ( 5) 5
i_spare5 Spare 5 2863 i1b 1
i_reflCor_atm Reflectivity Correction Factor For Atmospheric Effects 2864 i2b (4) 8
i_spare4 Spares 2872 i1b (160) 160

Page last updated: 01/11/13