%%% This codes helps to load the precipitation, one column array,
%%% data for the HW #3 for ATMO 529 class. 
%%% Basic script by A.O.



%%% loads the database
load precipmonthly_usmx.asci

%%% assigns the database a shorter variable name
d=precipmonthly_usmx;

%%% removes the original database to free memory
clear precipmonthly_usmx;


%%%% The following lines of code will help to place the
%%%% database in a 3D array


l=1;    %%% index


for k=1:660,         %%%% loop on the months
    for j=1:51,      %%%% loop on the latitude range
        for i=1:81,  %%%% loop on the longitude range
           P(i,j,k) = d(l);
           l=l+1;    %%%% increases the index in the databse by one unit
        end
    end
end


%%% calculates the mean and standard deviations ingnoring the -999.9 values


for i=1:81,
    for j=1:51,
        %% get the indexes for the cells with numbers different from -999.9
        q=find(P(i,j,:) ~= -999.9);   %this returns an array    
        % Uses the good data only to compute the mean and std (as defined
        % in Matlab)
        meanP(i,j) = mean(P(i,j,q));
        
        % standard deviation normalizes by N (uses flag =1 as second
        % arument). If normalization by N-1 is required, change flag=1 for
        % flag=0 or remove the second argument.
        stdP(i,j)  = std(P(i,j,q),1);  
    end
end



%%% now we create a latitude and longitude vectors
lon=(-140:1:-60);   % longitude from 140W to 60W
lat=(10:1:60);      % latitude from 10N to 60N

% meshgrid needed to be use together with pcolor.m or m_pcolor.m functions
[LON,LAT]=meshgrid(lon,lat);   
LON=LON'; LAT=LAT';   

%%%example of how to extract the data for a given month (here month=200)
A=P(:,:,200);    %%%   A is a 2D array

%%% plots the images for the computed mean and standard deviations

%%%%  
figure
imagesc(lon,lat,meanP',[0 200]);    %%%% plots data in the range 0 to 500 mm
colorbar;
axis xy;

%%% places the US/Mexico States boundaries on top

hold;     %%% holds the figure
plot_us_states(0,'black.',5,0);
fix_map('black',5,0)
plot_state('MX','black.',5,0)

title('Mean Precipitation in the contiguos US and Mexico');
xlabel('Longitude [deg]');
ylabel('Latitude [deg]');


figure
imagesc(lon,lat,stdP',[0 200]);    %%%% plots data in the range 0 to 500 mm
colorbar;
axis xy;

%%% places the US/Mexico States boundaries on top

hold;     %%% holds the figure
plot_us_states(0,'black.',5,0);
fix_map('black',5,0)
plot_state('MX','black.',5,0)

title('Standard deviation (1 \sigma) for Precipitation in the contiguos US and Mexico');
xlabel('Longitude [deg]');
ylabel('Latitude [deg]');