GARCE level03数据介绍
接触GARCE应用也有一段时间了，特别是毕设这段时间。
在这里我介绍一下两种不同机构发布的GARCE level 03数据，该级别的数据可以直接使用。
CSR（center for space research）空间研究中心发布的CSR GRACE/GRACE-FO RL06 Mascon Solutions (version 02)数据。
进入官网，可以找到不同种类的数据，我们要找的是CSR GARCE mascon数据。
具体什么是mascon数据，大家可以自己百度搜索一下。下载后，可以使用matlab读取一下文件内部的信息。使用一下代码查看文件信息：
ncdisp('CSR_GRACE_GRACE-FO_RL06_Mascons_all-corrections_v02.nc')；
得到以下的文件信息，我们一起解读一下
Format:【文件格式】
netcdf4_classic
Global Attributes:
Conventions = 'CF-1.6, ACDD-1.3, ISO 8601'
filename = 'netcdf/CSR_GRACE_GRACE-FO_RL06_Mascons_all-corrections_v02.nc'
Metadata_Conventions = 'Unidata Dataset Discovery v1.0'
standard_name_vocabulary = 'NetCDF Climate and Forecast (CF) Metadata Convention-1.6'
title = 'CSR GRACE and GRACE-FO MASCON RL06Mv2'
summary = 'Monthly mass anomaly grids from GRACE and GRACE-FO determined from CSR RL06 processing'
keywords = 'Solid Earth, Geodetics/Gravity, Gravity, liquid_water_equivalent_thickness'
keywords_vocabulary = 'NASA Global Change Master Directory (GCMD) Science Keywords'
platform = 'GRACE and GRACE-FO'
institution = 'The University of Texas - Center for Space Research (CSR)'
creator_name = 'Himanshu Save'
creator_email = 'grace@csr.utexas.edu'
creator_url = 'http://www2.csr.utexas.edu/grace'
creator_type = 'group'
creator_institution = 'UT-CSR'
publisher_name = ''
publisher_email = ''
publisher_url = ''
publisher_type = ''
publisher_institution = ''
project = 'NASA Gravity Recovery and Climate Experiment (GRACE) and NASA Gravity Recovery and Climate Experiment Follow-On (GRACE-FO)'
program = 'NASA Earth Science System Pathfinder and NASA Earth Systematic Missions Program'
url = 'https://doi.org/10.15781/cgq9-nh24'
id = '10.15781/cgq9-nh24'
naming_authority = 'org.doi.dx'
source = 'GRACE and GRACE-FO CSR RL06Mv2 Mascon'
processing_level = '2 and 3'
acknowledgement = 'GRACE is a joint mission of NASA (USA) and DLR (Germany). GRACE-FO is a joint mission of NASA (USA) and the German Research Center for Geosciences (GFZ). Use the digital object identifier provided in the id attribute when citing this data. See https://podaac.jpl.nasa.gov/CitingPODAAC'
license = 'https://science.nasa.gov/earth-science/earth-science-data/data-information-policy'
product_version = 'RL06 v2.0'
data_author = 'Himanshu Save (save@csr.utexas.edu)'
journal_reference = 'Save, H., S. Bettadpur, B. D. Tapley (2016), High resolution CSR GRACE RL05 mascons, J. Geophys. Res. Solid Earth'
time_epoch = '2002-01-01T00:00:00Z'
time_coverage_start = '2002-04-05T00:00:00Z'【该数据开始时间】
time_coverage_end = '2020-10-31T23:59:59Z'【结束时间】
geospatial_lat_min = '-89.875'
geospatial_lat_max = '89.875'
geospatial_lat_units = 'degrees_north'
geospatial_lon_min = '0.125'
geospatial_lon_max = '359.875'
geospatial_lon_units = 'degrees_east'
geospatial_lat_resolution = '0.25 degree grid; however the mascons are estimated on a 1-degree equal area mascons and the native resolution of the GRACE/GRACE-FO data is roughly 300km'
time_mean_removed = '2004.000 to 2009.999'【去除了这些年的平均值】
months_missing = '2002-06;2002-07;2003-06;2011-01;2011-06;2012-05;2012-10;2013-03;2013-08;2013-09;2014-02;2014-07;2014-12;2015-06;2015-10;2015-11;2016-04;2016-09;2016-10;2017-02;2017-02;2017-07;2017-08;2017-09;2017-10;2017-11;2017-12;2018-01;2018-02;2018-03;2018-04;2018-05;2018-08,2018-09'【缺失的月份，由于卫星的故障，后面绘制时间序列时比较关键】
postprocess_1 = 'RL06 AOD1B; OCEAN_ATMOSPHERE_DEALIAS_MODEL (GAD), MONTHLY_AVE, ADDED BACK TO OCEAN PIXELS ONLY'
postprocess_2 = 'Water density used to convert to equivalent water height: 1025 kg/m^3'
GIA_Removed = 'ICE6G-D; Peltier, W. R., D. F. Argus, and R. Drummond (2018) Comment on the paper by Purcell et al. 2016 entitled An assessment of ICE-6G_C (VM5a) glacial isostatic adjustment model, J. Geophys. Res. Solid Earth, 122.'
geocenter_correction = 'We use a version of TN-13 based on the CSR RL06 (https://podaac-tools.jpl.nasa.gov/drive/files/allData/grace/docs/TN-13_GEOC_CSR_RL06.txt)'
C_20_substitution = 'TN-14; Loomis et al., 2019, Geophys. Res. Lett., doi:10.1029/2019GL082929 (https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/TN-14_C30_C20_GSFC_SLR.txt)'
C_30_substitution = 'TN-14; Loomis et al., 2019, Geophys. Res. Lett., doi:10.1029/2019GL082929 (https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/TN-14_C30_C20_GSFC_SLR.txt)'
user_note_1 = 'The accelerometer on the GRACE-B spacecraft was turned off after August 2016. After this date, the accelerometer on GRACE-A was used to derive the non-gravitational accelerations acting on GRACE-B using a transplant procedure. This has led to a subsequent degradation in the quality of the gravity fields derived.'
user_note_2 = 'The accelerometer on the GRACE-FO 2 spacecraft has underperformed since after launch. The accelerometer on GRACE-FO 1 was used to derive the non-gravitational accelerations acting on GRACE-FO 2 using a transplant procedure. This has led to a degradation in the quality of the gravity fields derived.'
user_note_3 = 'Ellipsoidal correction has been applied. The grid is represented on the ellipsoid with semi-major axis of 6378.1363 km'
date_created = '2020-12-30T22:10:00Z'
variable = 'liquid water equivalent thickness'
label = 'RL06rc24cE'
Mask = 'Global'
Dimensions:
lat = 720
lon = 1440
time = 190
bounds = 2
Variables:
lat 【纬度】
Size: 720x1
Dimensions: lat
Datatype: single
Attributes:
units = 'degrees_north'
long_name = 'Latitude'
standard_name = 'Latitude'
axis = 'Y'
valid_min = '-89.875'
valid_max = '89.875'
bounds = 'lat_bounds'
lon 【经度】
Size: 1440x1
Dimensions: lon
Datatype: single
Attributes:
units = 'degrees_east'
long_name = 'Longitude'
standard_name = 'Longitude'
axis = 'X'
valid_min = '0.125'
valid_max = '359.875'
bounds = 'lon_bounds'
time 【累计研究月份190个月】
Size: 190x1
Dimensions: time
Datatype: single
Attributes:
units = 'days since 2002-01-01T00:00:00Z'
long_name = 'Time'
standard_name = 'Time'
axis = 'T'
calendar = 'gregorian'
bounds = 'time_bounds'
time_bounds 【包含年和月】
Size: 2x190
Dimensions: bounds,time
Datatype: single
lwe_thickness 【该变量就是我们需要读取的值了】
Size: 1440x720x190
Dimensions: lon,lat,time
Datatype: single
Attributes:
units = 'cm' 【单位是cm】
long_name = 'Liquid_Water_Equivalent_Thickness'
standard_name = 'Liquid_Water_Equivalent_Thickness'
coordinates = 'time lat lon'
grid_mapping = 'WGS84'
如果要读取lwe_thickness，并绘制图片，只需使用一下代码：
A=ncread('CSR_GRACE_GRACE-FO_RL06_Mascons_all
corrections_v02.nc','lwe_thickness');%%读取得到190层的数据
imagesc(A(:,:,100)) %%绘制第100个月的全球水储量等效水高
得到以下结果：
2.JPL（Jet Propulsion Laboratory）喷气推进实验室发布的Monthly Mass Grids - Global mascons (JPL RL06_v02)数据。【这个似乎要科学上网https://podaac.jpl.nasa.gov/dataset/TELLUS_GRAC-GRFO_MASCON_CRI_GRID_RL06_V2】
我们同样读取得到其文件内部的信息，比较一下两者的差别：
Format:
classic
Global Attributes:
Conventions = 'CF-1.6, ACDD-1.3, ISO 8601'
Metadata_Conventions = 'Unidata Dataset Discovery v1.0'
standard_name_vocabulary = 'NetCDF Climate and Forecast (CF) Metadata Convention-1.6'
title = 'JPL GRACE and GRACE-FO MASCON RL06Mv2 CRI'
summary = 'Monthly gravity solutions from GRACE and GRACE-FO as determined from the JPL RL06Mv2 mascon solution - with CRI filter applied'
keywords = 'Solid Earth, Geodetics/Gravity, Gravity, liquid_water_equivalent_thickness'
keywords_vocabulary = 'NASA Global Change Master Directory (GCMD) Science Keywords'
platform = 'GRACE and GRACE-FO'
institution = 'NASA/JPL'
creator_name = 'David Wiese'
creator_email = 'grace@podaac.jpl.nasa.gov'
creator_url = 'https://grace.jpl.nasa.gov'
creator_type = 'group'
creator_institution = 'NASA/JPL'
publisher_name = 'Physical Oceanography Distributed Active Archive Center'
publisher_email = 'podaac@jpl.nasa.gov'
publisher_url = 'https://podaac.jpl.nasa.gov'
publisher_type = 'group'
publisher_institution = 'NASA/JPL'
project = 'NASA Gravity Recovery and Climate Experiment (GRACE) and NASA Gravity Recovery and Climate Experiment Follow-On (GRACE-FO)'
program = 'NASA Earth Science System Pathfinder and NASA Earth Systematic Missions Program'
id = '10.5067/TEMSC-3JC62'
naming_authority = 'org.doi.dx'
source = 'GRACE and GRACE-FO JPL RL06Mv2-CRI'
processing_level = '2 and 3'
acknowledgement = 'GRACE is a joint mission of NASA (USA) and DLR (Germany). GRACE-FO is a joint mission of NASA (USA) and the German Research Center for Geosciences (GFZ). Use the digital object identifier provided in the id attribute when citing this data. See https://podaac.jpl.nasa.gov/CitingPODAAC'
license = 'https://science.nasa.gov/earth-science/earth-science-data/data-information-policy'
product_version = 'v2.0'
time_epoch = '2002-01-01T00:00:00Z'
time_coverage_start = '2002-04-16T00:00:00Z'
time_coverage_end = '2021-02-15T23:59:59Z'
geospatial_lat_min = -89.75
geospatial_lat_max = 89.75
geospatial_lat_units = 'degrees_north'
geospatial_lat_resolution = '0.5 degree grid; however the native resolution of the data is 3-degree equal-area mascons'
geospatial_lon_min = 0.25
geospatial_lon_max = 359.75
geospatial_lon_units = 'degrees_east'
geospatial_lon_resolution = '0.5 degree grid; however the native resolution of the data is 3-degree equal-area mascons'
time_mean_removed = '2004.000 to 2009.999'【移除的背景场时间一样】
months_missing = '2002-06;2002-07;2003-06;2011-01;2011-06;2012-05;2012-10;2013-03;2013-08;2013-09;2014-02;2014-07;2014-12;2015-06;2015-10;2015-11;2016-04;2016-09;2016-10;2017-02;2017-07;2017-08;2017-09;2017-10;2017-11;2017-12;2018-01;2018-02;2018-03;2018-04;2018-05;2018-08-2018-09'【缺失月份不太一样】
postprocess_1 = ' OCEAN_ATMOSPHERE_DEALIAS_MODEL (GAD), MONTHLY_AVE, ADDED BACK TO OCEAN PIXELS ONLY'
postprocess_2 = 'Water density used to convert to equivalent water height: 1000 kg/m^3'
postprocess_3 = 'Coastline Resolution Improvement (CRI) filter has been applied to separate land/ocean mass within mascons that span coastlines'
GIA_removed = 'ICE6G-D; Peltier, W. R., D. F. Argus, and R. Drummond (2018) Comment on the paper by Purcell et al. 2016 entitled An assessment of ICE-6G_C (VM5a) glacial isostatic adjustment model, J. Geophys. Res. Solid Earth, 122.'
geocenter_correction = 'We use a version of TN-13 based on the JPL mascons'
C_20_substitution = 'TN-14; Loomis et al., 2019, Geophys. Res. Lett., doi:10.1029/2019GL082929'
C_30_substitution = 'TN-14; Loomis et al., 2019, Geophys. Res. Lett., doi:10.1029/2019GL082929. This substitution is made for all months after August 2016.'
user_note_1 = 'The accelerometer on the GRACE-B spacecraft was turned off after August 2016. After this date, the accelerometer on GRACE-A was used to derive the non-gravitational accelerations acting on GRACE-B using a transplant procedure. This has led to a subsequent degradation in the quality of the gravity fields derived. The uncertainties in this file have been scaled to accomodate this degradation.'
user_note_2 = 'The accelerometer on the GRACE-D spacecraft began performing sub-optimally after June 21, 2018. After this date, the accelerometer on GRACE-C is used to derive the non-gravitational accelerations acting on GRACE-D using a transplant procedure. The uncertainties in the file have been scaled to accomodate this degradation using the current best state of knowledge.'
journal_reference = 'Watkins, M. M., D. N. Wiese, D.-N. Yuan, C. Boening, and F. W. Landerer (2015) Improved methods for observing Earth's time variable mass distribution with GRACE using spherical cap mascons, J. Geophys. Res., 120, doi:10.1002/2014JB011547. '
CRI_filter_journal_reference = 'Wiese, D. N., F. W. Landerer, and M. M. Watkins (2016) Quantifying and reducing leakage errors in the JPL RL05M GRACE mascon solution, Water Resour. Res., 52, doi:10.1002/2016WR019344. '
date_created = '2021-03-30T09:03:16Z'
history = '2021-04-25 09:41:29 GMT Hyrax-1.16.0 https://podaac-opendap.jpl.nasa.gov/opendap/allData/tellus/L3/mascon/RL06/JPL/v02/CRI/netcdf/GRCTellus.JPL.200204_202102.GLO.RL06M.MSCNv02CRI.nc.nc?lon%5B0:1:719%5D,lat%5B0:1:359%5D,time%5B0:1:193%5D,lwe_thickness%5B0:1:193%5D%5B0:1:359%5D%5B0:1:719%5D,uncertainty%5B0:1:193%5D%5B0:1:359%5D%5B0:1:719%5D,lat_bounds%5B0:1:359%5D%5B0:1:1%5D,lon_bounds%5B0:1:719%5D%5B0:1:1%5D,time_bounds%5B0:1:193%5D%5B0:1:1%5D'
Dimensions:【这个数据的分辨率只有0.5°×0.5°】
lon = 720
lat = 360
time = 194
bounds = 2
Variables:
lon
Size: 720x1
Dimensions: lon
Datatype: double
Attributes:
units = 'degrees_east'
long_name = 'longitude'
standard_name = 'longitude'
axis = 'X'
valid_min = 0.25
valid_max = 359.75
bounds = 'lon_bounds'
lat
Size: 360x1
Dimensions: lat
Datatype: double
Attributes:
units = 'degrees_north'
long_name = 'latitude'
standard_name = 'latitude'
axis = 'Y'
valid_min = -89.75
valid_max = 89.75
bounds = 'lat_bounds'
time 【时间范围比CSR发布的长一点】
Size: 194x1
Dimensions: time
Datatype: double
Attributes:
units = 'days since 2002-01-01T00:00:00Z'
long_name = 'time'
standard_name = 'time'
axis = 'T'
calendar = 'gregorian'
bounds = 'time_bounds'
lwe_thickness
Size: 720x360x194
Dimensions: lon,lat,time
Datatype: double
Attributes:
units = 'cm'
long_name = 'Liquid_Water_Equivalent_Thickness'
standard_name = 'Liquid_Water_Equivalent_Thickness'
coordinates = 'time lat lon'
grid_mapping = 'WGS84'
_FillValue = -99999
valid_min = -1747.2543
valid_max = 770.368
comment = 'Coastline Resolution Improvement (CRI) filter is applied'
uncertainty 【多了一个不确定性】
Size: 720x360x194
Dimensions: lon,lat,time
Datatype: double
Attributes:
units = 'cm'
long_name = 'uncertainty'
standard_name = 'uncertainty'
coordinates = 'time lat lon'
grid_mapping = 'WGS84'
_FillValue = -99999
valid_min = 0.15867
valid_max = 53.3447
comment = '1-sigma uncertainty: not for each 0.5 degree grid cell, but for each 3-degree mascon estimate'
lat_bounds
Size: 2x360
Dimensions: bounds,lat
Datatype: double
Attributes:
long_name = 'latitude boundaries'
units = 'degrees_north'
comment = 'latitude values at the north and south bounds of each pixel'
lon_bounds
Size: 2x720
Dimensions: bounds,lon
Datatype: double
Attributes:
long_name = 'longitude boundaries'
units = 'degrees_east'
comment = 'longitude values at the west and east bounds of each pixel'
time_bounds
Size: 2x194
Dimensions: bounds,time
Datatype: double
Attributes:
long_name = 'time boundaries'
units = 'days since 2002-01-01T00:00:00Z'
comment = 'time bounds for each time value, i.e. the first day and last day included in the monthly solution'
