function get_latest_met(info)
% get_latest_met(info)
%
% Last modified:  Time-stamp: <2004-10-13 09:42:30 haines>
%
% Abstract: Function that loads, appends new data, and saves with all data 
%
% Usage: get_latest_met(info)
  
% Processing steps
% (1) load previous month and current month data from netCDF 
% (2) append current to previous
% (3) subset data for latest 6 hours near top of the hour
% (4) calc u and v, and air_pressure_at_sea_level, and other times
% (5) create and write new text file of data to be encoded for NDBC
%     one for each hour record

% Author: Sara Haines, Oct 11, 2004
  
  have_this_month = 0;
  have_prev_month = 0;
  
  x = dir([info.ncdir '/*.nc']);
  for i=1:length(x)
    % x(i).name
    if strfind(x(i).name, [info.platform_name '_' info.month_str '.nc'])
      have_this_month = 1;
      ncfile_this_month = [info.ncdir '/' x(i).name];
    elseif strfind(x(i).name, [info.platform_name '_' info.prev_month_str '.nc'])
      have_prev_month = 1;
      ncfile_prev_month = [info.ncdir '/' x(i).name];
    end
  end
  
  % have_this_month
  % have_prev_month
  
  % (1) load previous and current months of data 
  
  if (have_this_month & have_prev_month)
    % if have both append this month data to previous month data
    nc_prev = netcdf(ncfile_prev_month, 'nowrite');
    nc_this = netcdf(ncfile_this_month, 'nowrite');

    % get variables
    % (2) append current to previous
    dn = [nc_prev{'time'}(:); nc_this{'time'}(:)];
    % size(dn)
    
    awspd = [nc_prev{'WSPDA'}(:); nc_this{'WSPDA'}(:)];
    awdir = [nc_prev{'WDIRA'}(:); nc_this{'WDIRA'}(:)];
    wgust = [nc_prev{'WGSTA'}(:); nc_this{'WGSTA'}(:)];
    atemp = [nc_prev{'ATEMP'}(:); nc_this{'ATEMP'}(:)];

    rh = [nc_prev{'RH'}(:); nc_this{'RH'}(:)];
    abaro = [nc_prev{'BARO'}(:); nc_this{'BARO'}(:)];
    
  elseif (have_this_month & ~have_prev_month)
    % if only this month just only use this month
    nc_this = netcdf(ncfile_this_month, 'nowrite');
    
    % get variables
    dn = nc_this{'time'}(:);
    % size(dn)
    
    awspd = [nc_this{'WSPDA'}(:)];
    awdir = [nc_this{'WDIRA'}(:)];
    wgust = [nc_this{'WGSTA'}(:)];
    atemp = [nc_this{'ATEMP'}(:)];

    rh = [nc_this{'RH'}(:)];
    abaro = [nc_this{'BARO'}(:)];

  else
    % if don't have, don't write out new netcdf file
    fprintf(2, ['... ... no current met data to read\n']);
  end
  
  % close the netcdf file
  if (have_this_month)
    nc_this = close(nc_this);
  end
  if (have_prev_month)
    nc_prev = close(nc_prev);
  end

  % (3) subset data
  if have_this_month
    dv = datevec(info.current_time_dn);
    dt = datenum([dv(1:4) 0 0]);
    hrs = [0:5]/24; % each hour for last 6 hours (minus two minutes) 
    target_times = (dt*ones(size(hrs))-hrs)-2/60/24;
    
    % datestr(target_times)
    
    which_latest = [];
    % for each target time find closest sample time within time limits (tl)
    for j=1:length(target_times)
      tt = target_times(j);
      tl1 = 15/60/24; % 15 minutes
      tl2 = 2/60/24; % 15 minutes
      xxx = abs(dn-tt);
      index_near = find( (dn >= tt-tl1) & (xxx == min(xxx)) & (dn <= tt+tl2) );
      if ~isempty(index_near)
	which_latest = [which_latest; index_near(1)];
      end
    end
        
    if ~isempty(which_latest)
      dn = dn(which_latest);
      
      % datestr(dn)
      
      awspd = awspd(which_latest);
      awdir = awdir(which_latest);
      wgust = wgust(which_latest);
      atemp = atemp(which_latest);

      rh    = rh(which_latest);
      abaro = abaro(which_latest);
      
      % set missing values to NaN
      params = {'awspd'; 'awdir'; 'wgust'; 'atemp'; 'rh'; 'abaro'};
      [nRows, nCols] = size(params);
      for j=1:nRows
	% whichMiss = find(awspd == -9999);
	% awspd(whichMiss) = deal(NaN);
	param_str = char(params(j));
	eval(['whichMiss = find(' param_str ' <= -9999);'])
	eval([param_str '(whichMiss) = deal(NaN);'])
      end
      
      % (4) calculations and other time variables for output
      
      % (4a) dew point from relative humidity
      
      % calc in situ saturation vapor pressure from Buck [1981] from
      % in situ temperature and static pressure (<rh>, <atemp> and <abaro>) 
      % of the air at the humidity sensor:
      
      a = 17.368;
      b = 238.88;

      es = 6.1121*( 1.0007 + (3.46e-06*abaro) ) .* exp( a*atemp./(atemp+b) );
      
      alpha = (es.*rh)/611;
      adewp = ( (b*log(alpha))./(a-log(alpha)) );
      
      % (4a) uv wind components (northward and eastward)
      r=pi/180;
      WVE = awspd .*(sin((awdir-180)*r));
      WVN = awspd .*(cos((awdir-180)*r));

      % (4b) air pressure at sea level
      
      % this procedure from class notes from Grant Petty
      % http://rain.aos.wisc.edu/~gpetty/aos330/lab1_slp_adjust.pdf
      atempK = atemp+273.1; % units deg K
      Rd = 287.1; % gas constant for dry air (Rd) units of J/(kg K)
      g = 9.807; % gravitional force units of m/s^2
      
      z0 = info.baro_ht; % height of measurement of abaro
      
      H = (Rd.*atempK)/g; 
      % scale height depending on air temperature
      % air pressure at sea level units of mbar quivalent to hPa (hecto-Pascal)
      abaro_sealevel = abaro.*(exp(z0./H));
      xxx=abaro_sealevel;
      % [abaro(1:10) abaro_sealevel(1:10)]
      
      % (4c) time variables for wind product exercise
      %     (i) seconds since  1970-1-1 00:00:00 UTC
      seacoos_time_1970 = (dn-datenum(1970, 1, 1, 0, 0, 0))*24*60*60;
      seacoos_time_1970 = round(seacoos_time_1970);

      %     (ii) matlab datenum (source_time)
      % don't need to do anything. 
      % dn
      
      %     (iii) date_time_string
      date_time_string = datestr(dn,'yyyy-mm-dd HH:MM:SS' );
    end
  end
  
  % for each target time
  for j=1:length(which_latest)
    [Y, M, D, H, Mi, Se] = datevec(dn(j));
    file_timestamp_str = sprintf('%04d%02d%02d_%02d%02d', Y, M, D, H, Mi);
    % fprintf('%s\n', file_timestamp_str);
    ndbcfile = [info.out_dir '/ndbc-input-' info.station '-' file_timestamp_str ...
		'-CMAN'];
    % if we have not sent this record yet 
    if ~exist([ndbcfile '_sent'], 'file')
      % and we have data then create and write ndbcfile
      if have_this_month
	disp([' ... ... ' ndbcfile])
	fid = fopen(ndbcfile, 'w');     
	ndbc_write;
	fclose(fid);    
      end
    end % 

  end % for j=1:length(which_latest)
    
%   % delete old file of latest data
%   if exist(ndbcfile, 'file')
%     delete(ndbcfile);
%   end
  
%   % (5) create ndbc input file
%   if have_this_month
%     fid = open(ndbcfile);     
%     ndbc_create;
%     close(fid);    
%   end