#HADAT TROPICS
 #TTS (channel 3)  around 220 hPa (~10 km or 1-35 km).
 #T2LT mean altitude 2.5 km (about 740 hPA);  
 #T2 - mean altitude 6.1 km) 466 hPa
	#http://www.sensorsone.co.uk/altitude-pressure-units-conversion.html 
 #effective T2LT altitude is 2.5 km, about 750 hPa (Christy)
 #TLS is centered around 75 hPa (~20 km or ~14-50 km) and TTS (channel 3)  around 220 hPa (~10 km or 1-35 km).
 # url="http://hadobs.metoffice.com/hadat/hadat2/hadat2_monthly_zonal.txt"
	#monthly from 1958; 5 degree latitude zones

get.hadat.trp=function() {
	url="http://hadobs.metoffice.com/hadat/hadat2/hadat2_monthly_tropical.txt"
	hadat=read.table(url,skip=19)
	names(hadat)=scan(url,skip=17,n=11,what="")
	hadat=ts(hadat[,3:11],start=c(hadat[1,2],1),freq=12)
	temp= (hadat== -999); hadat[temp]=NA
	#hadat[1,]
	#850hPa 700hPa 500hPa 300hPa 200hPa 150hPa 100hPa  50hPa  30hPa 
	#   0.4    0.4    0.6    0.4    0.3    0.0    0.7    1.5    2.0 
	#http://hadobs.metoffice.com/hadat/
	#id=dimnames(hadat)[[2]];n=nchar(id)
	#alt=as.numeric(substr(id,1,n-3))

	hadat.t2lt.trp= apply(hadat[,c("850hPa","700hPa")],1, function(x) weighted.mean(x,c(.33,.67))
 )
	 #effective T2LT altitude is 2.5 km, about 750 hPa (Christy)
	hadat.t2lt.trp=ts (hadat.t2lt.trp,start=1958,freq=12)

	return(list(hadat.t2lt.trp,hadat))
}