[gradsusr] Moisture Convergence?

[Ricardo Hallak]

Hi, Giacomo. 

1) I would suggest you to try low levels between 1000 and 700 hPa to see which one gives you the most significant signal, according your objectives. 

2) As your mixr is multiplied by 1000, it must have units of grams per kilograms (please, display mixr to see if it is g/kg: something like 1, 5, 10, 20 g/kg is the expected magnitude for mixr in g/kg). So, the units of mconv is just (g/kg)/s, that is, how much water vapor in grams (in each kilogram of ar) is converging or diverging in each second on a point (x,y) at that level. 

3) The answer is yes. Probably, the td field given by your (dynamical) model is more consistent than the "fitted curve" given by the formula in the script, which needs a lot of combinations between variables. 

Hope this helps, 
Ricardo 

----- Mensagem original -----

| Hi, I've found a grads script for calculating Moisture Convergence
| (mconv.gs)
| But I have 3 questions:

| 1)I have to set a level: which one should I use? Maybe 1000 hPa?

| 2)Which is the unit of measure of moisture convergence? Which range
| of values could I use (for example 0 to ?? And by steps of?)

| This is the script:
| * This is a script for displaying moisture convergence
| * Written by Michael Maxwell
| *
| * rh    = Relative Humidity in %
| * t     = Temp at *set level in degrees Kelvin
| * tc    = Temp in degrees C
| * td    = Dewpoint at *set level in degrees C
| * e     = Vapor pressure
| * mixr  = Mixing ratio
| * u     = U-wind in m/s
| * v     = V-wind in m/s
| * mconv = moisture convergence/divergence. convergence is positive
| and divergence is negative.

| 'tc = (t-273.16)'
| 'td = tc-((14.55+0.114*tc)*(1-0.01*rh) +
| pow((2.5+0.007*tc)*(1-0.01*rh),3) +
| (15.9+0.117*tc)*pow((1-0.01*rh),14))'
| 'vapr = 6.112*exp((17.67*td)/(td+243.5))'
| 'e = vapr*1.001+(lev-100)/900*0.0034'
| 'mixr = 0.62197*(e/(lev-e))*1000'
| 'mconv = (-1)*hdivg(u*mixr,v*mixr)*1e4'
| 'd mconv' 3)Could I delete "td", since WRF-NMM already gives me it?

| Thanks, Giacomo

| _______________________________________________
| gradsusr mailing list
| gradsusr at gradsusr.org
| http://gradsusr.org/mailman/listinfo/gradsusr
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20151019/7dea135a/attachment.html