Google Earth engine - merra-2 m2t1nxaer: aerosol daily data set from 1980 to 2022

M2T1NXAER（ or tavg1_2d_aer_Nx） It is the review, analysis, research and application version of the modern era 2 (MERRA-2) Time averaged two-dimensional data collection per hour . This set includes assimilated aerosol diagnostics , For example, aerosol composition （ Black carbon 、 dust 、 Sea salt 、 Sulfate and organic carbon ） Column mass density of 、 Surface mass concentration and total extinction of aerosol components （ And scattering ） Aerosol optical thickness (AOT) stay 550 nm. total PM1.0、PM2.5 and PM10 have access to   The formula described in the FAQ leads to

Data fields are used from 00:30 UTC Timestamp the central time of the first hour , for example ：00:30、01:30、...、23:30 UTC.

MERRA-2 yes NASA Global modeling and assimilation Office (GMAO) Using the Goddard earth observation system model (GEOS) edition 5.12.4 The latest version of global atmospheric reanalysis in the satellite era . This data set covers 1980 Years to date , The follow-up update is delayed for about one month 3 Zhou .

Dataset availability

1980-01-01T00:00:00Z–2022-05-31T23:00:00

Data set provider

NASA /MERRA

Earth engine fragment

ee.ImageCollection("NASA/GSFC/MERRA/aer/2")

Band information ：

The resolution of the
69375 rice

Y The resolution of the
55000 rice

Band

full name	Company	describe
BCANGSTR		Black carbon angstrom parameter [470-870 nm]
BCCMASS	kg /（ rice ^2）	Mass density of black carbon column
BCEXTTAU		Black carbon extinction AOT [550 nm]
BCFLUXU	kg / rice / second	Black carbon pillar u Wind mass flux
BCFLUXV	kg / rice / second	Black carbon pillar v- Wind mass flux
BCSCATAU		Black carbon scattering AOT [550 nm]
BCSMASS	kg /（ rice ^3）	Surface mass concentration of black carbon
DMSCMASS	kg /（ rice ^2）	Dms Column mass density
DMSSMASS	kg /（ rice ^3）	Dms Surface mass concentration
DUANGSTR		Dust parameters [470-870 nm]
DUCMASS25	kg /（ rice ^2）	Mass density of dust column - PM2.5
DUCMASS	kg /（ rice ^2）	Mass density of dust column
DUEXTT25		Remove dust AOT [550 nm] - PM2.5
DUEXTTAU		Remove dust AOT [550 nm]
DUFLUXU	kg / rice / second	Dust column u Wind mass flux
DUFLUXV	kg / rice / second	Dust column v- Wind mass flux
DUSCAT25		Dust scattering AOT [550 nm] - PM2.5
DUSCATAU		Dust scattering AOT [550 nm]
DUSMASS25	kg /（ rice ^3）	Dust surface mass concentration - PM2.5
DUSMASS	kg /（ rice ^3）	Dust surface mass concentration
OCANGSTR		Organic carbon parameters [470-870 nm]
OCCMASS	kg /（ rice ^2）	Mass density of organic carbon column
OCEXTTAU		Organic carbon extinction AOT [550 nm]
OCFLUXU	kg / rice / second	Organic carbon column u- Wind mass flux
OCFLUXV	kg / rice / second	Organic carbon column v- Wind mass flux
OCSCATAU		Organic carbon scattering AOT [550 nm]
OCSMASS	kg /（ rice ^3）	Surface mass concentration of organic carbon
SO2CMASS	kg /（ rice ^2）	So2 Column mass density
SO2SMASS	kg /（ rice ^3）	So2 Surface mass concentration
SO4CMASS	kg /（ rice ^2）	SO4 Column mass density
SO4SMASS	kg /（ rice ^3）	SO4 Surface mass concentration
SSANGSTR		Sea salt angstrom parameter [470-870 nm]
SSCMASS25	kg /（ rice ^2）	Mass density of sea salt column - PM2.5
SSCMASS	kg /（ rice ^2）	Mass density of sea salt column
SSEXTT25		Sea salt extinction AOT [550 nm] - PM2.5
SSEXTTAU		Sea salt extinction AOT [550 nm]
SSFLUXU	kg / rice / second	Sea salt column u Wind mass flux
SSFLUXV	kg / rice / second	Sea salt column v- Wind mass flux
SSSCAT25		Sea salt scattering AOT [550 nm] - PM2.5
SSSCATAU		Sea salt scattering AOT [550 nm]
SSSMASS25	kg /（ rice ^3）	Surface mass concentration of sea salt - PM2.5
SSSMASS	kg /（ rice ^3）	Surface mass concentration of sea salt
SUANGSTR		SO4 Angstrom parameter [470-870 nm]
SUEXTTAU		SO4 extinction AOT [550 nm]
SUFLUXU	kg / rice / second	SO4 column u- Wind mass flux
SUFLUXV	kg / rice / second	SO4 column v- Wind mass flux
SUSCATAU		SO4 scattering AOT [550 nm]
TOTANGSTR		Total aerosol angstrom parameter [470-870 nm]
TOTEXTTAU		Total aerosol extinction AOT [550 nm]
TOTSCATAU		Total aerosol scattering AOT [550 nm]

Code ：

var dataset = ee.ImageCollection('NASA/GSFC/MERRA/aer/2')
                  .filter(ee.Filter.date('2022-02-01', '2022-02-02'));
var black_carbon_column_u_wind_mass_flux = dataset.select('BCFLUXU');
var bccVis = {
  min: -0.0000116,
  max: 0.0000165,
  palette: ['001137', '01abab', 'e7eb05', '620500']
};
Map.setCenter(-95.62, 39.91, 2);
Map.addLayer(black_carbon_column_u_wind_mass_flux, bccVis);

quote ：

Terms of use

NASA Promote and research and application communities 、 private enterprise 、 Academia and the public share all data comprehensively and openly .

result ：

 

  The common calculation formula mentioned above pm：

1.  MERRA-2 What are the soil moisture variables and their units ？

MERRA-2 It provides two different units of soil moisture in the land surface diagnostic file set （M2T1NXLND、M2TMNXLND and M2TUNXLND）.

The first set of variables is the relative saturation of different layer depths （ Dimensionless ） The unit of g round Wet value (GWET*)（ See below for more details ）. The value is 1 Indicates completely saturated soil , The value is 0 It means completely anhydrous soil

The second set of variables is based on m 3 /m 3 The volume unit of represents the soil moisture content ( * MC ) , That is, large pieces of soil （ Including all solid substances 、 Water and air ） Volume of water in volume .

read more ”

2.  Why is the snow depth constant and similar in many times and places （~0.17 M ）？

Snow depth (SNODP) Only the depth of snow in the snow covered part is recorded . On the other hand , The amount of snow (SNOMAS) It is recorded relative to the whole grid cell area , Including snow and snow free parts .

The whole grid cell （ Including snow and snow free parts ） The average snow depth can be determined by SNODP And FRSNO Multiply to calculate .

read more ”

3.  MERRA-2 What is the radius of the aerosol in each container ？

single click “ Read more ” To see MERRA2（ And the current version GEOS/GOCART） Aerosol size used in .

Read more ”

4.  How to be in MERRA-2 Get the surface PM2.5 concentration ？

Use 2D aer_Nx Fields in the collection , The following formula can be used to calculate the particle concentration ：
PM2.5 = DUSMASS25 + OCSMASS+ BCSMASS + SSSMASS25 + SO4SMASS* (132.14/96.06)

Sulfate requires a multiplication factor , because MERRA-2 The species tracer in is sulfate ion . about GEOS FP Users of , Please note that this formula does not apply to FP, because MERRA-2 Nitrate aerosols are not included .

See resources »

5.  How to get MERRA-2 Medium PM1 and PM10 concentration ？

And PM2.5 Different ,PM2.5 The contribution of dust and sea salt is contained in 2D aer_Nx Collection ,MERRA-2 There's no ready-made PM1/PM10 The diagnosis . however , According to aer_Nv Calculation of aerosol mass mixing ratio in the set P1/PM10 concentration . From the lowest model layer 72 The aerosol mass mixing ratio in starts （ memories ：MERRA-2 The vertical layers are arranged from top to bottom ） And calculate the particle concentration according to the following formula ：

PM1 = (1.375*SO4 + BCphobic + BCphilic + OCphobic + OCphilic + 0.7 * DU001 + SS01 + SS002) * Edens

PM10 = (1.375*SO4 + BCphobic + BCphilic + OCphobic + OCphilic + DU001 + DU002 + DU003 + 0.74 * DU004 + SS01 + SS002 + SS003 + SS004) * Edens

among g Is the gravitational constant ,delp Is the pressure thickness of the lowest model layer （ With Pa In units of ）.

See resources »

6.  ASM and ANA What is the difference between data collection , How to choose ？

see also ANA and ASM Supplementary description of the differences between data collection [PDF].

7.  When data is available ？

Create a monthly file at the end of the month , Conduct quality inspection all month . After approval , The data will be published to GES DISC. therefore , Each new moon is about next month 15 solstice 20 Available between days .

however , If there is any interruption in the input observation flow or computing service , There may be a delay .

8.  What data is being generated ？

MERRA -2 Document specification document Provides relevant variables 、 Extensive information about units and data file collections .

9.  FLX The collection and LND What is the difference between the flux data contained in the set ？

MERRA The parameterization of land is Randy Koster Of Catchment Model , But other surfaces , Such as inland waters 、 The ocean surface and glaciers are also considered as sub grid blocks . stay LND In the variable set , All data are from land models , It is not weighted according to the land proportion of the grid point . These data are provided to better calculate the land budget of soil water and land energy .

FLX、RAD Or the data in any other variable set represents the grid box average of all different tiles weighted by their scores . This is where you will use evaporation to calculate the atmospheric energy balance . The important difference here is LND Just land , All other sets represent the entire grid box .

GEOS and MERRA Some land cover in is discussed more here ： https ://gmao.gsfc.nasa.gov/reanalysis/MERRA/land_fractions.php

10.  Why? MERRA And other reanalysis 1000MB and 850MB There is such a big difference between ？

Used to generate MERRA Of GEOS Data assimilation systems do not （ Or there is no ） Extrapolate the data to a pressure level higher than the surface pressure . These grid points are marked by undefined values . The result is , Compared with other datasets , The average area containing these points will not be representative without additional screening . Time average （ For example, monthly average ） There may also be significant differences at the edge of the terrain . Provide the lowest model level data and surface data , So that users can make their own inferences . Provides a page to discuss this issue . see MERRA

11.  What is the displacement height ,DISPH？

The choice for a more complete derivation and discussion is the micrometeorology textbook , for example Roland Stull Of 《 Boundary layer meteorology 》.

In short , Elements of the earth's surface 、 The grass 、 shrub 、 Crops 、 Trees and buildings will cause some friction and disturbance to the wind profile . Displacement height （ Or depth , Or zero plane displacement ） Their influence in calculating the wind profile of surface logging is explained . The displacement height is the height at which the logarithmic wind profile projects the wind to zero , Used to calculate the subsequent turbulent flux on the surface . At a height less than the displacement , Different physical processes and theories replace the logging profile method . For practical purposes ,MERRA 2m and 10m The output is intended for comparison with screen level weather stations .

12.  MERRA-2 What surface meteorological data have been assimilated ？

From the land-based ground meteorological station , Only ground pressure is assimilated . Radiosonde stations may contribute to lower level analysis （T、Qv、U、V）. Again , Commercial aircraft can provide lower levels of ascent and descent data （T、U、V）. And wind profiler （U,V）. On the ocean , Ships and buoys can provide PS、T、Qv、U and V. For more information , see also MERRA-2 Observation technical memorandum .