Geoscience Reference
In-Depth Information
127°
123°
119°
115°
111°
107°
103°
99°
95°
91°
87°
83°
79°
75°
71°
67°
10
11
12
13
14
15
16
10.3
11
14
45°
15
45°
16
12
16
13
14
14
15
16
17
16
41°
41°
15
17
18
17
19
20
37°
37°
16
21
22
33°
33°
23
24
24.6
29°
29°
All-season
PMP
estimate
(for 6 hours,
200 miles
2
)
19
17
20
18
21
22
25°
25°
23
24
24.6
119°
115°
111°
107°
103°
99°
95°
91°
87°
83°
79°
75°
Figure 14.10
All season average probable maximum precipitation calculated in inches (1 inch = 25.4 mm) for the eastern
USA for a 6 hour period and an area of 518 km
2
. (From Smith, 1993; after Hanson
et al
., 1982, published with permission.)
Spatial correlation of precipitation
In hydrometeorology and hydroclimatology, spatial analyses of precipitation are of
interest as a means for studying the dominant precipitation-producing mecha-
nisms and prevailing moisture flows in a region. For example, if an analysis was
made of the correlation between the precipitation measured at a point with that
measured at progressively increasing distances, it might be possible to deduce
information about average storm size and typical storm separation. For example,
consider a correlation analysis across a featureless plain for a period when there
was no consistent direction of air flow and precipitation was produced by ran-
domly located convective storms. In this case the spatial pattern of the correlation
might reveal concentric rings of positive correlation whose width reflected the
spatial dimensions of storms, and areas of negative correlation whose diameter
reflected the separation between storms (Fig. 14.11).
In more usual conditions such a plot of correlation coefficient can reveal evidence
of the prevailing direction of rain-bearing winds and of the location of features in the
landscape that are associated with atmospheric activity that generates precipitation.
