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Current Epoch: Epoch 10

Start: 16 Dec 2021 (Day 350) 14:27:41 | End: Present

Active Release: R05

R04 products will be available until all R05 products have been released.

CloudSat Epoch Information

Epoch 10

After a second reaction wheel anomaly on 26 August 2020 CloudSat returned to operation in December of 2021 in ACT-TWO (Attitude Control Through Two Wheel Operations) DO-Op (Daylight-Only Operations) mode, no longer in formation with CALIPSO.

Start: 16 Dec 2021 (Day 350) 14:27:41
End: 19 September 2023 (Day 262) 15:26:30

Epoch 09

Starting on July 5th, 2019 and continuing through August 26th, 2020, the apparent height of the surface in the radar profiles is not consistent with the Digital Elevation Map (DEM) that has been used with all CloudSat operational products throughout the mission. The mismatch is a result of an error in the satellite pointing or timing data or both. While still under investigation, the present the cause has not been isolated. Rather than further delaying the release of these data, they are being released as-is with the pointing/timing error. Fundamentally, this means there is a substantially larger uncertainty in the location where the radar beam intersects the surface that may be as large as 10 km.

Start: 11 Jul 2019 (Day 192) 00:00:00
End: 26 Aug 2020 (Day 239) 19:25:23

Epoch 08

CloudSat is joined by CALIPSO, forming the C-Train.

Start: 10 Oct 2018 (Day 283) 00:00:00
End: 10 Jul 2019 (Day 191) 23:59:59

Epoch 07

CloudSat exited the A-Train on February 22nd, 2018 after a reaction wheel anomaly.

Start: 3 May 2018 (Day 123) 07:25:00
End: End: 10 Oct 2018 (Day 283) 00:00:00

Epoch 06

Although CloudSat continues to only operate during the sunlit portion of the orbit, epoch 06 started when CloudSat returned to the A-Train formation on May 15th, 2012. Data products once again use MODIS and CALIPSO ancillary data although the overlap with CALIPSO is degraded because fewer formation flying maneuvers are performed.

Start: 15 May 2012 (Day 136) 00:49:00
End: 12 Jan 2018 (Day 12) 15:15:56

Epoch 05

A battery anomaly on April 17th, 2011 caused the spacecraft to stop collecting data and lose formation with the A-Train. The radar was turned back on in November 2011 and now collects data only during the sunlit portion of the orbit. Epoch 05 represents this new operating paradigm. In addition, the spacecraft remained outside of the A-Train formation so all data products were processed in radar-only mode without MODIS or CALIPSO data. The impact of the missing MODIS data on the CloudSat products is still being assessed and the combined radar/lidar products (2B-GEOPROF-LIDAR, 2B-CLDCLASS-LIDAR, and 2B-FLXHR-LIDAR) are not available.

Start: 27 Oct 2011 (Day 300) 23:28:21
End: 15 May 2012 (Day 136) 00:49:00

Epoch 04

Marks the beginning of a period where the CPR pulse rate will be periodically reduced, or increased, to manage the power draw on the battery (due to the reduced power margin as the battery ages). The increased or reduced pulsing with induce a slight change in sensitivity. The number of pulses can be found in the 1B-CPR field RayStatus_pulsesTx. The pulse rate will likely continue to be adjusted, seasonally, for the duration of the mission.

Start: 15 Feb 2011 (Day 46) 18:06:30
End: 17 Apr 2011 (Day 107) 18:17:31

Epoch 03

Epoch 02 ended when a battery anomaly forced the CPR offline. It was brought back into operations with a slightly reduced pulse rate that decreases the radar sensitivity by approximately 0.25 dB. Epoch 03 tags the modified operating parameters.

Start: 15 Jan 2010 (Day 15) 18:24:56
End: 15 Feb 2011 (Day 46) 18:06:30

Epoch 02

Increased specular reflection due to the nadir-pointing instrument caused an increase in ground clutter, so the spacecraft orientation was changed again so that the CPR pointed 0.16 degrees in the forward (along-track) direction.

Start: 15 Aug 2006 (Day 227) 20:56:31
End: 7 Dec 2009 (Day 341) 11:43:22

Epoch 01

The pointing error was corrected and the spacecraft was oriented so that the CPR pointed to nadir.

Start: 7 Jul 2006 (Day 188) 14:14:02
End: 15 Aug 2006 (Day 227) 20:56:31

Epoch 00

During the initial phase of the mission it was unknown that the CPR was pointing off-nadir 1.7021 degrees in the forward (along-track) direction and 0.1314 degress to the right (across-track).

Start: 2 Jun 2006 (Day 153) 13:42:23
End: 7 Jul 2006 (Day 188) 14:14:02

2C-SNOW-PROFILE

Product Availability: Full mission availability except for anomalies and maneuver data gaps

Captioned Figure 1
An example plot showing vertical profiles of snowfall rate using 2C-SNOW-PROFILE.

The CloudSat Snow Profile product (2C-SNOW-PROFILE) provides estimates of vertical profiles of snowfall rate along with snow size distribution parameters and snow water content for radar reflectivity profiles observed by the CloudSat Cloud Profiling Radar (CPR) which, based on an evaluation of the profile and ancillary data, appear to coincide with snow at the surface. For these profiles, the product also estimates snowfall rate at the surface. Because of ground clutter, the CPR cannot reliably measure reflectivities near the surface. To overcome this limitation, the product algorithm estimates snow properties using a truncated reflectivity profile, terminated somewhat above the surface, then uses the estimated snow properties in the bottom-most portion of the profile to estimate the surface snowfall rate. For the truncated reflectivity profile, profiles of size distribution parameters are retrieved using an optimal estimation algorithm which incorporates a priori information about snow microphysical properties, radar scattering properties, and size distribution parameters. Retrievals are performed only for profiles which appear likely to contain snow at the surface, either dry snow or snow with a small melted mass fraction. The retrieved size distribution parameter profiles and the a priori information are then used to calculate profiles of snowfall rates and snow water contents. The optimal estimation method produces uncertainty estimates for the retrieved size distribution parameters, and these uncertainties are then used to estimate uncertainties for the snowfall rates and snow water contents.

Primary Publication(s)

Wood, N. B., T. S. L'Ecuyer, A. J. Heymsfield, G. L. Stephens, D. R. Hudak, and P. Rodrigues, 2014: Estimating snow microphysical properties using collocated multisensor observations. J. Geophys. Res. Atmos., 119, 8941-8961, doi:10.1002/2013JD021303.

Wood, N. B., T. S. L'Ecuyer, F. L. Bliven, and G. L. Stephens, 2013: Characterization of video disdrometer uncertainties and impacts on estimates of snowfall rate and radar reflectivity, Atmos. Meas. Tech., 6, 3635-3648, doi:10.5194/amt-6-3635-2013.

  • 2C-SNOW-PROFILE P1_R05 (Current)
  • 2C-SNOW-PROFILE P_R04

Process Description and Interface Control Document (PDICD)

2C-SNOW-PROFILE P1_R05 PDICD (Rev. 0) (Updated May 1, 2018)
E09 Data Issues (Updated January 30, 2023)

Process Description and Interface Control Document (PDICD)

2C-SNOW-PROFILE P_R04 PDICD (Updated February 10, 2013)

Algorithm Specifications (for latest R05)

Geolocation Fields

Field Type Dimensions Units Valid Range Missing Missing Op. Factor Offset
Profile_time FLOAT32 nray seconds [0.0, 6000.0] 1.0 0.0
UTC_start FLOAT32 scalar seconds [0.0, 86400.0] 1.0 0.0
TAI_start FLOAT64 scalar seconds [0.0, 600000000.0] 1.0 0.0
Latitude FLOAT32 nray degrees [-90.0, 90.0] 1.0 0.0
Longitude FLOAT32 nray degrees [-180.0, 180.0] 1.0 0.0
Height INT16 nbin,nray 109 [-5000, 30000] -9999 == 1.0 0.0
DEM_elevation INT16 nray meters [-9999, 8850] 9999 == 1.0 0.0
Vertical_binsize FLOAT32 scalar 109 -9999.0 == 1.0 0.0

Data Fields

Field Type Dimensions Units Valid Range Missing Missing Op. Factor Offset
snowfall_rate FLOAT32 nbin,nray mm/h [0.0, 40.0] -999.0 == 1.0 0.0
snowfall_rate_uncert FLOAT32 nbin,nray mm/h [0.0, 120.0] -999.0 == 1.0 0.0
log_N0 FLOAT32 nbin,nray -- [2.0, 8.0] -999.0 == 1.0 0.0
log_N0_uncert FLOAT32 nbin,nray -- [1.0, 2.0] -999.0 == 1.0 0.0
log_lambda FLOAT32 nbin,nray -- [-1.0, 2.0] -999.0 == 1.0 0.0
log_lambda_uncert FLOAT32 nbin,nray -- [0.0, 1.0] -999.0 == 1.0 0.0
snow_water_content FLOAT32 nbin,nray g/m^3 [0.0, 5.0] -999.0 == 1.0 0.0
snow_water_content_uncert FLOAT32 nbin,nray g/m^3 [0.0, 15.0] -999.0 == 1.0 0.0
Data_quality UINT8 nray -- [0, -1] 1.0 0.0
Data_status UINT16 nray -- [0, -1] 1.0 0.0
Data_targetID UINT8 nray -- [0, -1] 1.0 0.0
RayStatus_validity UINT8 nray -- [0, -1] 1.0 0.0
Navigation_land_sea_flag UINT8 nray -- [1, 4] 1.0 0.0
snow_retrieval_status INT8 nray -- [-128, 127] 0 == 1.0 0.0
norm_chi_square FLOAT32 nray -- [0.0, 10.0] -999.0 1.0 0.0
snowfall_rate_sfc FLOAT32 nray mm/h [0.0, 40.0] -999.0 == 1.0 0.0
snowfall_rate_sfc_uncert FLOAT32 nray mm/h [0.0, 120.0] -999.0 == 1.0 0.0
snowfall_rate_sfc_confidence INT8 nray -- [-1, 4] -1 == 1.0 0.0
snow_top_height_bin INT8 nray -- [1, 125] -99 == 1.0 0.0

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