Question

Consider the following with respect to 'double-mass curve'
1. Plot of accumulated rainfall with respect to two chronological orders
2. Plot for estimating multiple missing rainfall data
3. Plot for checking the consistency of the rainfall data
4. Plot of accumulated annual rainfall of a station vs. accumulated rainfall of a group of stations

Which of these statements are correct?

• A. 1 and 3
• B. 2 and 3
• C. 3 and 4
• D. 1 and 4

Answer 1

The correct option is C 3 and 4

Double mass curve is a plot for checking the inconsistency of the rainfall data. This technique is based on the principle that when each recorded data comes from the same parent population, they are consistent. In this technique the data of the annual (or monthly mean) rainfall of any station $x$ and also the average rainfall of the group of base stations covering a long period is arranged in reverse chronological order (i.e. the latest record as the first entry and the oldest record as the last entry in the list). The accumulated precipitation of the station x ($\sum P_x$) and the accumulated values of the average of the group of base stations, ($\sum P_{av}$) are calculated starting from the latest record values of $\sum P_x$ and are plotted against $\sum P_{av}$ for various consecutive time periods.