WMOD00584

• Title: Use of Nested Models to Simulate Regional Orographic Precipitation
• Date: 11/1/1992
• Weather Modification - Doc Type: Report

a

OCTOBER - DECEMBER 1982-83

2500

-

~ 2000

---

- MM4 Model
-H- Gauges> 2700 m msl
Gauge$2100 to 2700 m msl
-I:- Gauges < 21 OO:m msl

c
o
jg 1500
0..
.0
Q)
L-
a..
Q) 1000
>
~
::J
E 500
::J
o

~

o
Date 0

J

Month

b

JANUARY - DECEMBER 1988

800

L

~

A

_700 - MM4 Model
E
.s 600 -H- Gauges:> 2700 m msl
c
0 Gauges 2100 to 2700 m msl
~ 500
- Gauges < 2100 m msl
.5.. -I::-
.0 400
Q)
L-
a:.
Q) 300
>
+=
<\1
"S 200
E
::J
0 100
0 J D

Figure 3. Time-series of cumulative precipitation predicted by MM4 and
corresponding observations in the Gunnison Basin during: <a> the El Nino 1982-83
and (b) dry 1988-89 periods. Three elevation zones stratify the observed data
clearly demonstrating the effect of elevation on precipitation during both periods.
MM4 predictions closely matched observed cumulative precipitation above -2700 m msl
in 1983 from October to mid-May; however, the model grossly overestimated
precipitation during the convective summer months. In 1988, MM4 predicted light
precipitation that matched the low elevation observations from January to March,
then its estimate increased sharply and exceeded all observations in mid-April,
again indicating a problem in predicting convective precipitation.