chapter 3 precipitation

Question 1

Parameters defining rainfall

Answer 1

1. Intensity or rate of precipitation: the depth of water per unit of time in m/s, mm/min, or inches/hour.
2. Duration of precipitation in seconds, minutes or hours.
3. Depth of precipitation expressed as the thickness of a water layer on the surface in mm or inches.
4. Area (the geographic extent of the rainfall in km2).
5. Frequency of occurrence, usually expressed by the ‘return period’ e.g. once in 10 years.

Question 2

rainfall storms can be distinguished by their

Answer 2

meteorological characteristics (convective, orographic, frontal, cyclonic).

Question 3

rainfall storms can be distinguished by their meteorological characteristics (convective, orographic, frontal, cyclonic). Another way to characterize storms is from a statistical point of view. Distinction is made between

Answer 3

• exterior statistics
• interior staistics

Question 4

exterior statistics

Answer 4

refer to total depth of the storm, duration of the storm, average intensity of the storm and time between storms;

Question 5

interior statistics

Answer 5

• refer to the time and spatial distribution of rainfall rate within storms.

Question 6

The exterior statistics can generally be described by ………………………………………, which can be………………………… and ……………………dependent.

Answer 6

probabilistic distributions, seasonally, spatially

Question 7

Depth is related to

Answer 7

duration

Question 8

a long duration is associated with

Answer 8

a large depth

Question 9

average high intensity is related to

Answer 9

short duration

Question 10

for given ………………….and …………………………….some type of storms gave similar histories of ……………………………

Answer 10

locations, climatic conditions, rainfall accumulation

Question 11

convective storms have

Answer 11

highest intensity at the beginning of the storm

Question 12

tropical cyclones have (intensity)

Answer 12

largest intensity in the middle of the storm

Question 13

compare between tropical cyclones and thunderstorms

Answer 13

tropical cyclones have a much longer storm duration and larger rainfall depth

Question 14

methods to estimate the average rainfall over an area (areal rainfall)

Answer 14

1. Average depth method
2. Thiessen method
3. Isohyetal method

Question 15

convection storm (duration and extent)

Answer 15

a short duration and a small areal extent; hence, the ARF decreases steeply with distance.

Question 16

Frontal storm (duration and area of influence)

Answer 16

long duration and large area of influence. ARF, hence, is expected to decrease more slowly with distance.

Question 17

cyclones (duration and extent)

Answer 17

long durations and a large areal extent

Question 18

ARF curve comparison between convective storm, cyclonic storm and orographic storm

Answer 18

convective storm: steepest

cyclonic storm: moderate slope

orographic storm: more moderate slope

Question 19

analyse, however, and what has particular relevance for ……………………………….., is the occurrence of dry spells

Answer 19

rainfed agriculture

Question 20

rainfed agriculture seldom succeeds without

Answer 20

supplementary irrigation.

Question 21

In view of the small water retaining capacity of the …………, a dry spell of more than ………………….days already causes serious damage to the crop

Answer 21

soil, five