How to measure rainfall

The rain gauge consists of a water receiver (funnel), a water storage cylinder (outer cylinder) and a water storage bottle, and is equipped with a special measuring cup proportional to its caliber.

I. Installation

Placed on a fixed shelf in the observation field. The opening of the device is kept horizontal, and the height from the ground is 70cm. In areas with deep snow in winter, spare shelves should be installed nearby, so that the height of the rain gauge mouth from the ground can reach 1.0- 1.2 meters. When the snow depth exceeds 30 cm, the instrument should be moved to the standby frame for observation.

When it snows in winter, the funnel must be unscrewed from the device mouth (the station of the old rain gauge must be replaced by the snow mouth), the water storage bottle should be taken away, and the precipitation should be directly filled by the snow mouth and the water storage bucket.

Two. Observe and record

(1) liquid precipitation observation records the precipitation before observation at 8: 00 and 20: 00 every day 12 hours. During observation, replace the water storage bottle, take the replaced water storage bottle back indoors (or in the observation field when the precipitation is less or has stopped), and pour the water into the measuring cup (pay attention to emptying). Then, hold the upper end of the measuring cup with your index finger and thumb and let it hang freely (or put the measuring cup on a horizontal table). The line of sight is flush with the water surface, and the number of scales read is the precipitation, which is recorded in the precipitation time column of the observation book. When the precipitation is normal, it can be measured by fractions and summed. After the measurement, it should be rechecked. In addition, it can also be weighed directly with a platform scale.

(2) Observation record of solid precipitation Replace the water storage cylinder with the spare water storage cylinder, cover it, take it back indoors, and measure it with a cup after the solid precipitation melts. You can also weigh the solid sediment together with the water storage tank with a platform scale, and remove the sediment and the soil attached to the tank before weighing. If there is no platform scale, under observation, a certain amount of warm water can be added to completely melt the solid precipitate, and then measured with a cup, but the measured value must be deducted from the amount of warm water added. Observation time and record are the same as liquid precipitation.

(3) Send the observation record of precipitation for 6 hours to the station equipped with telemetering rain gauge. The telemetering rain gauge is used to observe the precipitation for 6 hours before 2 o'clock, 8 o'clock, 14 o'clock and 20 o'clock, and recorded in the RR column of the observation record book. If there is no telemetering rain gauge or the telemetering rain gauge fails, the precipitation in the first six hours should be observed with the rain gauge, and the record should be recorded in the RR column of the observation book; At the same time, according to the provisions of the above (a), recorded in the 8 o'clock and 20 o'clock time columns respectively.

(4) Handling of several special situations

1. In hot and dry days, after the precipitation stops, make up the measurement in time, and the measured results should be recorded in the RR column or timing column of the next planned observation, depending on whether the remote rain gauge is used (supplementary observation is needed when serving, and the processing method is the same).

2. If there is no precipitation during and before the precipitation observation at 20 o'clock, there will be precipitation from then on to 20 o'clock (including the next day); Or there is precipitation at 20 o'clock and before observation, but the precipitation just ends at or before 20 o'clock. In case of the above two situations, a supplementary observation of precipitation should be made at 20 o'clock on the hour, and recorded in the precipitation timing column at 20 o'clock on the same day, so that the weather phenomenon is consistent with the precipitation record.

When there is a snowstorm, we should observe the precipitation.

4. When there is no precipitation, the precipitation column is blank. The precipitation less than 0.05 mm is 0.0. The amount of pure fog, dew, frost, ice needle, fog and snow blowing is treated as no precipitation, but the amount of snow blowing must be measured to calculate evaporation.