Agricultural drought index and monitoring on national scale
LU HouquanNational Meteorological Center, CMA
Contents• Agricultural drought disasters in China• Agricultural drought indices
--Precipitation anomalies --Soil moisture--Remote sensing drought index--Crop Water Deficit Index--Integrated Drought Index
• Integrated agricultural drought monitoring
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19501954195819621966197019741978198219861990199419982002
year
Percentage(%)
The area of cropland damaged by drought was on the range from 40% to 80%,occupying that caused by weather disasters(Data from the National Statistic Bureau)
Part 1: Agricultural drought disasters in China
Agricultural drought with seasonal and regional feature in China
Due to:• Several climate types (uneven distribution of
precipitation on spatial and temporal, large variability)
• Various agriculture styles in different regions (crop varieties, cropping system, water requirement for various crops)
• Different water supply conditions for agricultural crops
Seasonal agricultural drought• Spring drought: impacting on winter wheat and other
crops sowing in northern China, and impacting on rice transplanting in southern China
• Early summer drought: impacting on some crops sowing and autumn-matured crops in northern China
• Midsummer drought: impacting on rice in southern China• Autumn drought: impacting on winter wheat sowing in
North China• Winter drought: impacting on over-winter crops in South
China
Part 2: Agricultural drought indices
The main factors related with agricultural drought
• Climate (evaportranspiration, precipitation)
• Soil (type, moisture)
• Crops (species, stage of development)
• Irrigation capacity (facilities , water resource)
--Precipitation anomalies (PA)
Pa is percentage of precipitation anomalies(%); is climatic normal of precipitation (mm) of the 30 days ,P is precipitation of 30 days (mm)
• Advantage: observable, denoting storage of water for agriculture, especially for rainfed farming
• Disadvantage: can’t reflect water consumption and water demand of crops
Agricultural drought index
%100
PPPPa
P
Agricultural drought index-- Relative soil moisture (RSM)
Rw is relative soil moisture(%);W is soil moisture on weight percentage(%),fc is field capacity(%)
• Advantages : measurable and simulated, expressing how much available water in soil for crops
• Disadvantage: with a poor representativeness on spatial, can not be use to paddy field
%100cfwRw
Agricultural drought index--Crop Water Deficit Index (CWDI)
• CWDIi is crop water deficit index of 10 days, ETa is actual evapotranspiration of 10 days, P and I is precipitation and irrigation of 10 days, ai is weight coefficient
• Advantages: to judge if precipitation and irrigation could meet the water demand of crops or not
• Disadvantage: unmeasured, can’t express other factors influence on water consumption and with many coefficients
a
ai ET
IPETCWDI
n
iii CDWIaCDWI
1
Crop water requirement
ETa= Kc·ETo
ETa = crop water consumption (evapotranspiration)Kc = crop coefficientETo = reference crop evapotranspiration
• FAO Penmen-Monteith Equation for ETo
Rn = net radiation at crop surfaceG = soil heat fluxT = mean daily air temperature at 2 m heightU2 = wind speed at 2 m heightes - ea = saturation vapour pressure deficit∆ = slope vapour pressureγ= psychrometric constant
)34.01(
)(273
900)(408.0
2
2
U
eeUT
GRET
asn
o
--Remote sensing drought indices
Integrated by Thermal Inertia method, Crop Water Stress Index ,Temperature and Vegetation Drought Index
• Advantages: observable, continuously on spatial, reflecting status of soil moisture and crops response to water supply
• Disadvantage: impacted by cloudy and vegetations on ground, data source unstable
n
iii wfDRG
1
Agricultural drought index
--Integrated Drought Index
• For various regions and cloud status, precipitation anomalies, soil moisture, CWDI and remote sensing indices would be given different weighting.
Agricultural drought index
n
iii DIfIDI
1
Agro-climatic zoning of China
LAI
Kc
CNDI weight
Remote Sensing
Precipitation anomalies
Crops water deficit
Soil moisture
Integrated drought index
In Soil –plant-atmosphere continuum , overall agricultural drought monitoring
Part 3: Integrated agricultural drought monitoring
Flow chart
Soil moisture Index
Crop water deficitIndex
Remote SensingDrought Index
Dynamic soil moisture model
Dynamic CWDIDrought model
Remote SensingDrought model
Soil moistureSoil textureCrop stage
Mete. dataCrop stage
NOAA、EOS/MODIS、FY-1、FY-2C
Integrated agricultural drought model on region scale
Agricultural drought monitoring system on GIS
Agricultural drought monitoring operation
Products of Agricultural drought monitoring
Mete. data
Precipitationanomalies
Moving preci.anomalies
On the GIS, integrated agricultural drought monitoring system
Surface agricultural drought monitoring system
Remote sensing monitoring system
Integrated monitoring system
Case on 1st decade Aug.2006
Remote Sensing
Soil moisture
Integrated monitoring
Crop water deficit
Soil moisture simulation
Remote Sensing
Soil moisture Crop water deficit
Integrated monitoring
Precipitation anomalies
Case on 1st decade Jan. 2009
Agricultural drought monitor and prediction on national scale product released by NMC