This standard specifies the calculation method, classification standard, nomenclature, and usage of the meteorological drought index. This standard is applicable to drought monitoring, assessment, and scientific research in the fields of meteorology, hydrology, agriculture, forestry, and social economy. GB/T 20481-2006 Meteorological Drought Grade GB/T20481-2006 Standard download decompression password: www.bzxz.net
This standard specifies the calculation method, classification standard, nomenclature, and usage of the meteorological drought index. This standard is applicable to drought monitoring, assessment, and scientific research in the fields of meteorology, hydrology, agriculture, forestry, and social economy.

ICS 07.060
National Standard of the People's Republic of China
GB/T20481-—2006
Classification of meteorological drought061214000014
Published on August 28, 2006
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Administration of Standardization of the People's Republic of China
Implementation on November 1, 2006
2 Terms and definitions
3 Individual meteorological drought index
3.1 Precipitation anomaly percentage
Relative humidity index
Standardized precipitation index
Soil relative moisture drought index
3. 5 Palmer drought index
4 Comprehensive meteorological drought index
4.1 Comprehensive meteorological drought grade
4.2 Calculation method of comprehensive meteorological drought index4.3 Determination and evaluation of drought process
4.4 Annual report of meteorological drought grade monitoring
Appendix A (informative appendix)
Appendix B (normative appendix)
Appendix D (normative appendix)
Annual report of meteorological drought monitoring
Calculation method of possible evapotranspiration
Calculation method of standardized precipitation index
Calculation method of Palmer drought index
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GB/T 20481--2006
Appendix A of this standard is informative, and Appendix B, Appendix C and Appendix D are normative. This standard is proposed by the China Meteorological Administration.
This standard is under the jurisdiction of the Policy and Regulations Department of the China Meteorological Administration. -iKAoNiKAca
GB/T 20481-—2006
This standard was drafted by the National Climate Center, with participation from the China Meteorological Science Academy, the National Meteorological Center, and the Forecasting and Disaster Reduction Department of the China Meteorological Administration.
The main drafters of this standard are: Zhang Qiang, Zou Xukai, Xiao Fengjin, Lv Houquan, Liu Haibo, Zhu Changhan, An Shunqing, Shan
GB/T20481—2006
Drought is one of the major natural disasters in my country, with the characteristics of high frequency, long duration, and wide range. The frequent occurrence and long-term persistence of droughts not only bring huge losses to the national economy; they also cause adverse effects such as water shortages, increased sandstorms, intensified desertification, and deterioration of the ecology and environment. In recent years, with the continuous intensification of global warming, drought events have also shown a clear upward trend.
Long Over the years, meteorological workers have conducted a lot of research on drought and its indicators. However, due to the large climate differences in different regions and the uneven development of technical strength of meteorological departments at all levels, there are often great differences in the use of drought indicators, drought classification, monitoring and assessment of drought occurrence and impact. It is difficult to make temporal and spatial comparisons and meet the needs of people's governments at all levels to organize the prevention of meteorological disasters. Therefore, this standard aims to standardize the drought indicators and methods used nationwide, which are comparable in space and time and objectively describe the process of drought occurrence, development, persistence and relief, as well as the degree and pattern of drought occurrence, so as to standardize and standardize the national drought monitoring and assessment business. Drought problems are very complex and involve a wide range of areas. They can be divided into meteorological drought, agricultural drought, hydrological drought and economic and social drought. Meteorological drought is the basis of other professional drought research and business. The meteorological drought grades formulated in this standard are suitable for use by meteorological, hydrological, agricultural, forestry, social economy and other industries engaged in drought monitoring and assessment departments. The main technical methods of this standard are drought indicators and methods that are commonly used, simple, objective, scientific and highly operational in drought monitoring and assessment business at home and abroad. The meteorological drought index is divided into five levels, namely no grass, light drought, moderate drought, severe drought and very early drought. 1 Scope
Meteorological drought level
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GB/T20481—2006
This standard specifies the calculation method, level classification standard, level naming, and usage of the meteorological drought index. This standard is applicable to drought monitoring, assessment operations and scientific research in the fields of meteorology, hydrology, agriculture, forestry, and social economy. 2 Terms and definitions
The following terms and definitions apply to this standard. 2.1
Precipitation
precipitationS
The depth of the liquid or solid (after final melting) water layer falling from the cloud to a single-valued area plane (assuming no leakage, evaporation, loss, etc.), the unit of precipitation is millimeter (m) in the form of snow, sleet, box, ice, ice particles and ice needles. Note: Precipitation includes rain,
airtemperature
The physical quantity of the degree of air temperature, in degrees Celsius (2.3
Windspeed
The ratio of the distance traveled by air to the time required, in meters per second (m/s)P
Relative humidity
relative humiditybzxz.net
At the same temperature,
Sunshine hours
The ratio of the actual water vapor pressure to the saturated water vapor bed, expressed in white fraction (%).sunshine duration
The number of hours that the sun actually shines on the horizontal ground in one place, in hours (h)Possible evapotranspirationpotentfayeapotranspirationWhen the underlying surface is sufficiently moist
Millimeter (mm).
The evapotranspiration that can maintain sufficient supply is also called evaporative power or maximum possible evapotranspiration, in units of Note: This standard uses the FAO ManMionteith correction formula or Thornthwaite method recommended by the Food and Agriculture Organization of the United Nations to calculate possible evapotranspiration. For the calculation method, see Appendix B.
Relative soil moisturerelative soil moistureThe ratio of the actual soil moisture content to the field water holding capacity of the soil, expressed as a percentage (%). 2.8
Soil moisturesoil moisture
The percentage of the moisture content in the soil per unit volume or unit weight to the mass of the same volume or mass of soil after drying, expressed as a percentage (%).
Soil field water holding capacity
soil field capacity
GB/T 20481—2006
The maximum water content of capillary suspended water that a soil can hold. It is expressed as the percentage of water in the mass of the same volume or homogeneous soil after drying (%).
Relative moisture indexrelative moisture indexThe difference between the precipitation in a certain period and the possible evapotranspiration in the same period divided by the possible evapotranspiration in the same period. 2.11
Climaticnurmal
The half-mean of a meteorological element for 30 years or more. Note: This standard takes the average of the most recent 10 decades as the climatic mean according to the relevant provisions of the World Meteorological Organization. For example: for the period from 2901 to 2010, the climatic half-mean is the average of 30 years from 1971 to 2000. 2.12
Meteorological droughtThe phenomenon of water shortage caused by the imbalance between evaporation and precipitation in a certain period, where water expenditure is greater than water income. 2. 13
Meteorological drought index The meteorological drought index uses meteorological elements and indicators obtained by a certain calculation method to monitor or evaluate the degree of moisture shortage caused by abnormal weather and climate in a certain period of time in a certain area.
Meteorological drought category classification describes the degree of moisture shortage, that is, the classification of meteorological drought index. 2. 15
Drought occurrence
In a certain period of time, the precipitation is less than the climate average, the air is dry, or evaporation causes insufficient soil moisture, which has an adverse effect on the growth and development of vegetation. The meteorological drought level reaches the standard of mild drought or above. 2.16
Drought development Drought aggravation The precipitation in a certain period of time is continuously less than the climate average, the soil moisture is further reduced than the previous period, the impact on vegetation is more serious than the previous period, the intensity of meteorological drought is more severe than the previous period, and the meteorological drought level is at least one level more severe. 2.17
Drought persistence
Drought during a period of time, the precipitation and evaporation are basically balanced, the soil moisture shortage caused by the previous low precipitation still persists, the impact on vegetation is similar to that in the previous period, and the meteorological drought level is the same as that in the previous period. 2. 18
Draught alleviationDraught reliefNatural precipitation occurs, the soil moisture increases compared with the previous period, the impact on vegetation is alleviated compared with the previous period, and the meteorological drought level is at least one level lower than that in the previous period.
Drought relief
More natural precipitation occurs in a period of time, making the soil moisture reach a suitable or slightly wet state, and the meteorological drought level reaches zero or normal. 2.20
Percentage of precipitation anomaliesPercentage of precipitation anomaliesThe difference between the precipitation in a period of time and the average precipitation in the same period of normal years is expressed as a percentage of the average precipitation in the same period of normal years, expressed in percentage (%).
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GB/T 20481—2006
Climatically appropriate for existing condition precipltation (CAFEC Precipitation) The amount of precipitation required to maintain water resources that are compatible with the determined water use in a certain area, in millimeters (mm). 3 Single meteorological drought index
3. 1 Precipitation deviation percentage (P,)
Precipitation deviation percentage Meteorological drought grade (see Table 1) Table 1 Precipitation deviation percentage Dry grade classification table Grade
Calculation method of precipitation deviation percentage
Monthly scale
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