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Ma S.,CAS Changchun Observatory | Wang Q.,Institute of Meteorological science of Jilin Province | Yu H.,Agrometeorological Observatory of Yushu County | Xu L.,Agrometeorological Observatory of Yushu County | Zhang T.,Agrometeorological Observatory of Yushu County
Journal of Natural Disasters | Year: 2012

This paper studies the influence of spring drought on maize yield based on the combination tests of soil water stress test and field test of seeding trials. Results show that during the corn planting and emerging periods, the relationship between soil water content and corn yield follows a quadratic function. Spring water stress of soil on maize yield is very obvious. In field water capacity, soil humidity declied by 1 percentage points each, maize yield will be reduced by about 7% ; soil effective water reduction for every 10 mm,per unit area yield will drop about 14%. The article also identified maize drought index of soil moisture. The influence of soil moisture decrease on the corn yield was quantitatively studied. The indicator and mode of soil moisture influence on maise yield can be used for developing the assessment and prediction of maize spring drought, and can also be used to determine drought-resistant irrigation content. Source

Jiang X.,Institute of Plateau Meteorology | Yang S.,Sun Yat Sen University | Li J.,CAS Institute of Atmospheric Physics | Li Y.,Institute of Plateau Meteorology | And 2 more authors.
Climate Dynamics | Year: 2013

The NCEP Climate Forecast System version 2 (CFSv2) provides important source of information about the seasonal prediction of climate over the Indo-Pacific oceans. In this study, the authors provide a comprehensive assessment of the prediction of sea surface temperature (SST) in the tropical Indian Ocean (IO). They also investigate the impact of tropical IO SST on the summer anomalous anticyclonic circulation over the western North Pacific (WNPAC), focusing on the relative contributions of local SST and remote forcing of tropical IO SST to WNPAC variations. The CFSv2 captures the two most dominant modes of summer tropical IO SST: the IO basin warming (IOBW) mode and the IO dipole (IOD) mode, as well as their relationship with El Niño-Southern Oscillation (ENSO). However, it produces a cold SST bias in IO, which may be attributed to deeper-than-observed mixed layer and smaller-than-observed total downward heat flux in the tropical IO. It also overestimates the correlations of ENSO with IOBW and IOD, but underestimates the magnitude of IOD and summer IOBW. The CFSv2 captures the climate anomalies related to IOBW but not those related to IOD. It depicts the impact of summer IOBW on WNPAC via the equatorial Kelvin wave, which contributes to the maintenance of WNPAC in July and August. The WNPAC in June is mostly forced by local cold SST, which is better predicted by the CFSv2 compared to July and August. The mechanism for WNPAC maintenance may vary with lead time in the CFSv2. © 2013 Springer-Verlag Berlin Heidelberg. Source

Ma S.,CAS Changchun Observatory | Wang Q.,Institute of Meteorological science of Jilin Province | Lu H.,National Meteorological Center | Xu L.,Agrometeorological Observatory of Yushu County of Jilin Province | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Maize emergence speed and the emergence rate relate to soil moisture and air temperature, and they largely determine the corn growth and yield. In order to obtain the relationships between seedling emergence speed, seedling rate of spring maize (Zea mays) and soil moisture and air temperature respectively, the experiments of water stress and by-stage sowing for spring maize were conducted at an agro-meteorological experiment station in the central part of Northeastern China. In an artificial rain-proof cover, 4 water treatments (not drought, light drought, drought and severity drought) and 3 sowing treatments (early, middle and late) were set to create soil moisture variation and air temperature difference during the period from sowing to germination. And soil moisture, water amount for irrigation, rainfall, air temperature, the seedling stage and emergence rate were observed. The results showed that the relationships between soil moisture and emergence rate, period of emergence both were significantly quadratic function during the periods of sowing and emerging. Below field capacity, the greater soil moisture was, the faster the corn came out and the higher the emergence rate was. Soildrought delayed the period of emergence and decreased emergence rate. Low temperature slowed down the emergence, but had little effect on emergence rate. The equation of relationship between days from sowing to emerging (D), soil moisture (S) at a depth of 0 to 20 cm and average air temperature (T) was D = 63. 450-1. 194S -1. 442T. The equation of relationship between emergence rate (P), S and T was P =5. 107 S +1. 857 T-56. 5. Combinational influence indexes of average soil moisture, effective soil water (H) and air temperature on maize emergence speed were that corn emerged quickly when 25% >S>21%, 70 mm>H>45 mm and T>18°C; it would emerge normally when 21% >S>18%, 45 mm>H> 35 mm and 18°C >T>16. 5°C; and it would emerge slowly when 18% >S>16%, 35 mm>H> 25 mm and 16. 5 °C >T>15. 5 °C; and the emergence was postponed remarkably when S<16%, H<25 mm and T<15. 5 °C. Germination rate depended mainly on soil moisture in this study. The highest germination rate (more than 95%) occurred when S >85% and H > 50mm; the higher one (about 90%) when relative humidity was about 80% and 50 mm>H>40 mm; and the lower one when relative humidity was less than 70% and 50 mm>H>40 mm; and the one was less than 65% when relative humidity was less than 60% and H<30 mm, and the serious drought happened. Source

Liu X.,National Climate Center | Yang S.,Sun Yat Sen University | Li Q.,National Climate Center | Kumar A.,National Oceanic and Atmospheric Administration | And 2 more authors.
Climate Dynamics | Year: 2014

Subseasonal forecast skills and biases of global summer monsoons are diagnosed using daily data from the hindcasts of 45-day integrations by the NCEP Climate Forecast System version 2. Predictions for subseasonal variability of zonal wind and precipitation are generally more skillful over the Asian and Australian monsoon regions than other monsoon regions. Climatologically, forecasts for the variations of dynamical monsoon indices have high skills at leads of about 2 weeks. However, apparent interannual differences exist, with high skills up to 5 weeks in exceptional cases. Comparisons for the relationships of monsoon indices with atmospheric circulation and precipitation patterns between skillful and unskillful forecasts indicate that skills for subseasonal variability of a monsoon index depend partially on the degree to which the observed variability of the index attributes to the variation of large-scale circulation. Thus, predictions are often more skillful when the index is closely linked to atmospheric circulation over a broad region than over a regional and narrow range. It is also revealed that, the subseasonal variations of biases of winds, precipitation, and surface temperature over various monsoon regions are captured by a first mode with seasonally independent biases and a second mode with apparent phase transition of biases during summer. The first mode indicates the dominance of overall weaker-than-observed summer monsoons over major monsoon regions. However, at certain stages of monsoon evolution, these underestimations are regionally offset or intensified by the time evolving biases portrayed by the second mode. This feature may be partially related to factors such as the shifts of subtropical highs and intertropical convergence zones, the reversal of biases of surface temperature over some monsoon regions, and the transition of regional circulation system. The significant geographical differences in bias growth with increasing lead time reflect the distinctions of initial memory capability of the climate system over different monsoon regions. © 2013 Springer-Verlag Berlin Heidelberg. Source

Shen B.Z.,Institute of Meteorological science of Jilin Province | Shen B.Z.,Latitude | Lin Z.D.,CAS Institute of Atmospheric Physics | Lu R.Y.,CAS Institute of Atmospheric Physics | And 2 more authors.
Science China Earth Sciences | Year: 2011

Summer rainfall is vital for crops in Northeast China. In this study, we investigated large-scale circulation anomalies related to monthly summer rainfall in Northeast China using European Center for Medium-Range Weather Forecast ERA-40 reanalysis data and monthly rainfall data from 79 stations in Northeast China. The results show that the interannual variation in rainfall over Northeast China is mainly dominated by a cold vortex in early summer (May-June) and by the East Asian summer monsoon in late summer (July-August). In early summer, corresponding to increased rainfall in Northeast China, an anomalous cyclonic anomaly tilted westward with height appears to the northwest and cold vortices occur frequently. In late summer, the rainfall anomaly is mainly controlled by a northward shift of the local East Asian jet stream in the upper troposphere and the northwest extension of the western Pacific subtropical high (WPSH) in the lower troposphere. The enhanced southwesterly anomaly in the west of the WPSH transports more moisture into Northeast China and results in more rainfall. In addition, compared with that in July, the rainfall in Northeast China in August is also influenced by a mid- and high-latitude blocking high over Northeast Asia. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg. Source

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