使用Matlab实现Penman-Montieth蒸散发计算

clear all;
% set the data path
path='D:\matlabpractise\day\';
fnm='luoch53942.txt';

file1=[path,fnm];
data=load(file1);
dims=size(data);
row=dims(1);
col=dims(2);
Nt=row;

% define station information
LON=109.5;     % longititude of the station
LAT=35.817;      % latitude  of the station
alt=1159.8;       % altitude  of the station
h=10;             % hight of the wind speed

% define variables
year=data(:,2);
month=data(:,3);
day=data(:,4);
Pre=data(:,5)/100;           % mean air pressure of the day
Tmean0=data(:,6)/10;         % mean tempreture of the day
Tmax=data(:,7)/10;          % max tempreture of the day
Tmin=data(:,8)/10;          % min tempreture of the day
RH=data(:,9)/100;            % mean relative humidity of the day
RHmin=data(:,10)/100;        % min relative humidity of the day
P=data(:,11)/10;            % precipitation of the day
WS=data(:,12)/10;           % mean wind speed of the day

WSmax=data(:,13);        % max wind speed of the day
SD=data(:,17)/10;           % duration of sunshine  

% year series
yr_beg=1981;
yr_end=year(Nt);
Ny=yr_end-yr_beg+1;
yr_arr0=yr_beg:1:yr_end;
yr_arr=reshape(yr_arr0,Ny,1);

%%
% *********start to calculate the ET by Pemann-Montieth Equation***********
% ********step 1:mean daily tempreture********
% Tmean=zeros(Nt,1);
Tmean=(Tmax+Tmin)/2;   % Tmean in PM method
% ********step 2:wind speed********
  % u=WS*4.87/ln(67.8*h-5.42);in fact,ln is in format log:log=ln
    % h=10 £¬so 4.87/ln(67.8*h-5.42)=0.7480
u=WS*0.7480;

% ********step 3:slope of saturation vapor pressure curve********
delta=4098*0.6108*exp(17.27*Tmean./(Tmean+273.3))./(Tmean+273.3).^2;
% ********step 4:air pressure curve********
pre=Pre;        %  air pressure
% ********step 5:psychrometric constant********
gamma=6.65E-4*pre;     
%********step 6:Delta Term(DT)(auxiliary for calculation for Radiation Term)********
DT=delta./(delta+gamma.*(1+0.34*u));
% ********step 7:Psi Term(PT)(auxiliary for calculation for Wind Term)********
PT=gamma./(delta+gamma.*(1+0.34*u));