Opening a netcdf variable

Question

Arvind Gauns 2022-4-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1687334-opening-a-netcdf-variable

评论： Arvind Gauns 2022-4-3

I want to open a netcdf file and access the bariable for a particular region.

Iused the command ncdisp to open it. I got the following.

>> ncdisp(a)

Source:

F:\TROPOSIF\TROPOSIF_L2B_2021-09-30.nc

Format:

netcdf4

Global Attributes:

title = 'TROPOSIF_L2B'

date_created = '2021-10-19 19:46:12.428756'

Dimensions:

n_elem = 2460190

num_bd_rfl = 7

ncorner = 4

time = 1

Groups:

/METADATA/

Groups:

/METADATA/ALGORITHM_SETTINGS/

Attributes:

Polynomial degree win-743 nm = 3

Number SVs win-743 nm = 4

Fitting window win-743 nm (nm) = [743 758]

Polynomial degree win-735 nm = 3

Number SVs win-735 nm = 7

Fitting window win-735 nm (nm) = [735 758]

Cloud fraction threshold = 0.8

SZA threshold = 70

VZA threshold = 60

Quality level threshold = 80

SIF reference wavelength (nm) = 740

Masked-out spectral channels for SIF retrieval (#) = 179

FWHM of macro-channels for TOA reflectance = [3 3 3]

/PRODUCT/

Variables:

time

Size: 1x1

Dimensions: /time

Datatype: single

Attributes:

units = 'seconds since 2010-01-01 00:00:00'

standard_name = 'time'

comment = 'Reference time of the measurements. The reference time is set to yyyy-mm-ddT00:00:00 UTC, where yyyy-mm-dd is the day on which the measurements of a particular data granule start.'

long_name = 'reference start time of measurement'

delta_time

Size: 2460190x1

Dimensions: /n_elem

Datatype: int32

Attributes:

units = 'milliseconds since 2021-09-30T00:00:00 UTC'

standard_name = 'delta time'

comment = 'Time difference with time for each measurement'

long_name = 'offset from the reference start time of measurement'

SIF_743

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'retrieved SIF@740 743-758 nm fitting window'

long_name = 'retrieved SIF@740 (743-758nm)'

SIF_Corr_743

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'daylength-corr SIF@740 743-758 nm fitting window'

long_name = 'daylength-corr SIF@740 (743-758nm)'

SIF_ERROR_743

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = '1-sigma error 743-758 nm fitting window'

long_name = '1-sigma SIF retrieval error (743-758nm)'

SIF_735

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'retrieved SIF@740 735-758 nm fitting window'

long_name = 'retrieved SIF@740 (735-758nm)'

SIF_Corr_735

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'daylength-corr SIF@740 735-758 nm fitting window'

long_name = 'daylength-corr SIF@740 (735-758nm)'

SIF_ERROR_735

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = '1-sigma error 735-758 nm fitting window'

long_name = '1-sigma SIF retrieval error (735-758nm)'

latitude

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'latitude'

longitude

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'longitude'

Groups:

/PRODUCT/SUPPORT_DATA/

Groups:

/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/

Variables:

TOA_RFL

Size: 7x2460190

Dimensions: /num_bd_rfl,/n_elem

Datatype: single

Attributes:

units = '-'

standard_name = 'TOA Reflectance (cloud frac<0.2)'

long_name = 'TOA Reflectance at atmospheric windows within 665-785 nm'

WVL_RFL

Size: 7x1

Dimensions: /num_bd_rfl

Datatype: single

Attributes:

units = 'nm'

standard_name = 'WVL_RFL'

long_name = 'Spectral points at which TOA_RFL is calculated'

Mean_TOA_RAD_743

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'TOA Radiance'

long_name = 'Mean TOA Radiance in 743-758 nm fitting window'

Mean_TOA_RAD_735

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

units = 'mW/m2/sr/nm'

standard_name = 'TOA Radiance'

long_name = 'Mean TOA Radiance in 735-758 nm fitting window'

/PRODUCT/SUPPORT_DATA/GEOLOCATIONS/

Variables:

viewing_zenith_angle

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'viewing zenith angle'

solar_zenith_angle

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'solar zenith angle'

relative_azimuth_angle

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'relative azimuth angle'

latitude_bounds

Size: 4x2460190

Dimensions: /ncorner,/n_elem

Datatype: single

Attributes:

standard_name = 'latitude_bounds'

units = 'degrees_north'

comment = 'The four latitude boundaries of each ground pixel'

longitude_bounds

Size: 4x2460190

Dimensions: /ncorner,/n_elem

Datatype: single

Attributes:

standard_name = 'longitude_bounds'

units = 'degrees_east'

comment = 'The four longitude boundaries of each ground pixel'

/PRODUCT/SUPPORT_DATA/INPUT_DATA/

Variables:

cloud_fraction_L2

Size: 2460190x1

Dimensions: /n_elem

Datatype: single

Attributes:

standard_name = 'cloud_fraction'

LC_MASK

Size: 2460190x1

Dimensions: /n_elem

Datatype: uint8

Attributes:

units = '([ENF=1, EBF=2, DNF=3, DBF=4, MF=5, CS=6, OS=7, WS=8, S=9, G=10, PW=11, C=12, U=13, CNV=14, SI=15, B=16])'

standard_name = 'Land Cover Map (MODIS MCD12C1 2018)'

long_name = 'Land Cover Map'

I tried to follow the documentation as well as few tutorials available on youtube but that didnt help me resolve my doubts.

My queries are.

How to access the SIF_743 product ?
i want to plot the lat long and z parameter as SIF. which commands should I use ?
How to subset an area? i.e. belgium

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Answer 1

KSSV 2022-4-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1687334-opening-a-netcdf-variable#answer_933359

How to access the SIF_743 product

Read about ncread.

2. i want to plot the lat long and z parameter as SIF. which commands should i use ?

REad about scatter, pcolor,

How to subset an area? I,e belgium

Read about interp2, inpolygon.

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Arvind Gauns 2022-4-3

@KSSV

thank you for your response.

I tried ncread. It didnt help me to access the variable SIF_743. Which is the reason I posted the query. I followed the following references as well.

https://nl.mathworks.com/matlabcentral/answers/355920-how-to-open-netcdf4-file-in-matlab

https://www.youtube.com/watch?v=PJurb-IPKM8&t=141s

Once I am able to get throught the first question I will followup with the nest two.

Arvind Gauns 2022-4-3

@KSSV

for question 2

plot as in mapping. I know the scatter and the other function

The dataset is a global data for different parameters, I want to access one of the parameter. plot the map using the corresponding latitude and longitude and extract the desired value (from Belgium).

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