Hello, everyone.
I have downloaded the daily 2m temperature of ERA-40 dataset, it's .grib format. I want to calculate monthly max and min temperature, but now the data record four times a day , namely , 00:00:00,06:00:00,12:00:00 and 18:00:00. And the data ,such as september 1957, it's grib_struct format, which has 120 records, how should I write the script? Now , I can just read a record, I don't know how to write the loop? can anyone help me ? Thank you!
This is the script reading file, and attachment is the grib file.
>>grib_struct=read_grib('E:\_mars-webmars-public-svc-green-001-6fe5cac1a363ec1525f54343b6cc9fd8-R3BtDg.grib',-1);
>>dn=datenum(grib_struct(31).pds.year,grib_struct(31).pds.month,grib_struct(31).pds.day,grib_struct(31).pds.hour,grib_struct(31).pds.min,0);
>>datestr(dn,31)
>>grib_struct(31).gds
>>gds=grib_struct(31).gds;
>>lon=gds.Lo1:gds.Di:gds.Lo2;
>>lat=gds.La1:-gds.Di:gds.La2;
>>ThisUgrd=reshape(grib_struct(31).fltarray,gds.Ni,gds.Nj)';
% It has 120 records,but I don't know how to read them all once time? I can just read one record now.
>>pcolor(lon,lat,ThisUgrd)
>>R=makerefmat('RasterSize',size(ThisUgrd),'Latlim',[59 90],'Lonlim',[-74 -11])
>>[latlimits,lonlimits]=limitm(ThisUgrd,R)
%The folling scripts means that extracting temperature values from the grib.
>>lats=[72.58;75.1;71.3];
>>longs=[-34.48;-42.33;-26.7];
>>value=ltln2val(ThisUgrd,R,lats,longs)
Dear Saiping! I have shared two links given below with you, hopefully they shall be fit you in getting your answer. They might contribute a little portion in you required answer. Please go through them.
https://www.mathworks.com/help/thingspeak/calculate-high-and-low-temperatures.html
https://www.mathworks.com/matlabcentral/answers/172994-how-to-get-max-min-temp-data-from-hourly-data
Hello, Anand. Thanks for answering the question. Using groupsummary function is a good idea,it's convenient and time-saving. Howerver, I'm still confused how to extract the data into a table. The input data is in a grib_struct format, the stime is character string format, the coordinates are struct format and the variable value is in the fltarray item, it's double format. I don't know how to put them together into a table. Do you have a idea? Thank you again.
Hello, Meer. Thanks for answering the question. I'm trying the "Thingspeak " method. Actually my object file is 15 G, it's too large to read in the matlab , I hope it's successful in "Thingspeak",.Thank you again.
Hi, Vito. I just give three coordinates for test, so the result only shows three values. If you want more values, you can give more coordinates.
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