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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.

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.

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.

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.

Gao Z.,Institute of Meteorological science of Jilin Province | Gao Z.,Latitude | Hu Z.-Z.,5830 University Research Court | Jha B.,5830 University Research Court | And 6 more authors.
Climate Dynamics | Year: 2014

In this work, authors examine the variabilities of precipitation and surface air temperature (T2m) in Northeast China during 1948-2012, and their global connection, as well as the predictability. It is noted that both the precipitation and T2m variations in Northeast China are dominated by interannual and higher frequency variations. However, on interdecadal time scales, T2m is shifted significantly from below normal to above normal around 1987/1988. Statistically, the seasonal mean precipitation and T2m are largely driven by local internal atmospheric variability rather than remote forcing. For the precipitation variation, circulation anomalies in the low latitudes play a more important role in spring and summer than in autumn and winter. For T2m variations, the associated sea surface pressure (SLP) and 850-hPa wind (uv850) anomalies are similar for all seasons in high latitudes with significantly negative correlations for SLP and westerly wind anomaly for uv850, suggesting that a strong zonal circulation in the high latitudes favors warming in Northeast China. The predictability of precipitation and T2m in Northeast China is assessed by using the Atmospheric Model Inter-comparison Project type experiments which are forced by observed sea surface temperature (SST) and time-evolving greenhouse gas (GHG) concentrations. Results suggest that T2m has slightly higher predictability than precipitation in Northeast China. To some extent, the model simulates the interdecadal shift of T2m around 1987/1988, implying a possible connection between SST (and/or GHG forcing) and surface air temperature variation in Northeast China on interdecadal time scales. Nevertheless, the precipitation and T2m variations are mainly determined by the unpredictable components which are caused by the atmospheric internal dynamic processes, suggesting low predictability for the climate variation in Northeast China. © 2013 Springer-Verlag (outside the USA).

Sun L.,Institute of Meteorological science of Jilin Province | Sun L.,Latitude | Shen B.,Institute of Meteorological science of Jilin Province | Shen B.,Latitude | And 3 more authors.
Climate Dynamics | Year: 2016

A unique dataset of 53-year (1961–2013) rainfall measurements from 104 stations uniformly distributed in the Northeast China, combined with the observation-based NCEP/NCAR atmospheric reanalysis, is used to analyze the precipitation anomalies in Northeast China during late boreal summer (July–August) and their relationship with the anomalous moisture transport associated with the fluctuations of the East Asian Summer Monsoon (EASM) circulation. Based on this analysis, a new EASM influence index (IEASM) is proposed to quantify the EASM effects on the Northeast China summer precipitation. The relationship between the IEASM variations and patterns of the anomalous regional atmospheric circulation is demonstrated. The characteristics of several precursors that lead to the major fluctuations of the IEASM index are also explored. The results show that the EASM influence index is closely linked to the anomalous rainfall in Northeast China and can be used as a major factor to measure the physical processes that affect the regional dry and wet conditions. The IEASM index responds to the large-scale anomalies of the atmospheric circulation sensitively. Specifically, the high IEASM values are associated with the intensified Mongolia cyclone, blocking developing near the Ural Mountains and a northwestward shift of subtropical high over the western Pacific. The low IEASM values are associated with a reversed pattern of these features. The IEASM anomalous fluctuation has some precursors. A major high (low) index during the summer is likely preceded with the pattern of the sea surface temperature anomalies of an El Niño (La Niña) event in the Pacific from the previous early fall to early winter. © 2016 Springer-Verlag Berlin Heidelberg

Wu R.,Chinese University of Hong Kong | Yang S.,National Oceanic and Atmospheric Administration | Liu S.,Institute of Meteorological science of Jilin Province | Sun L.,Institute of Meteorological science of Jilin Province | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2011

A previous study revealed a close relationship between interannual variations of northeast China (NEC) summer temperature and a tripole sea surface temperature (SST) anomaly pattern in the North Atlantic in preceding spring. The present study investigates the change in the above relationship and the plausible causes for the change. A tripole SST index is defined with its positive value corresponding to positive SST anomalies in the tropics and midlatitudes and negative SST anomalies in the subtropics. The tripole SST anomaly pattern has a weak correlation with NEC summer temperature during the 1950s through the mid-1970s, in sharp contrast to the 1980s and 1990s. This change is related to the difference in the persistence of the tripole SST pattern. Before the late 1970s, the tripole SST pattern weakened from spring to summer, and thus, the spring North Atlantic tripole SST pattern had a weak connection with NEC summer temperature. On the contrary, after the late 1970s, the tripole SST pattern displayed a tendency of persistence from spring to summer, contributing to circulation changes that affected NEC summer temperature. There are two factors for the persistence of the tripole SST pattern from spring to summer. One is the North Atlantic air-sea interaction, and the other is the persistence of SST anomalies in the eastern equatorial Pacific during the decay of El Nio-Southern Oscillation (ENSO). It is shown that the North Atlantic SST anomalies can have an impact on NEC summer temperature independent of ENSO. Copyright © 2011 by the American Geophysical Union.

Wu R.,Institute of Global Environment and Society | Yang S.,National Oceanic and Atmospheric Administration | Liu S.,Institute of Meteorological science of Jilin Province | Sun L.,Institute of Meteorological science of Jilin Province | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

Northeast China (NEC) summer temperature tends to be lower (higher) than normal in El Nio (La Nia) developing years during 1950s through mid-1970s. The relationship between the NEC summer temperature and El Nio-Southern Oscillation (ENSO) is weakened or even becomes opposite in 1980s and 1990s. The present study documents this interdecadal change and investigates plausible reasons for this change. Before the late 1970s, ENSO affects the NEC summer temperature through modulating the South Asian heating and consequently the midlatitude Asian circulation. After the late 1970s, the connection between ENSO and the Indian summer monsoon and that between the South Asian heating and the midlatitude Asian circulation have been weakened. This leads to a weakening of ENSO impacts on the NEC summer temperature. It is found that the NEC summer temperature variations are closely related to the North Atlantic sea surface temperature (SST) and circulation changes in 1980s and 1990s. In particular, a tripole North Atlantic SST anomaly pattern in boreal spring is a good precursory for the NEC summer temperature anomalies. The NEC summer temperature displays a negative correlation with the summer SST surrounding the Maritime Continent in 1980s and 1990s. In many years, the tropical North Pacific and the North Atlantic SST anomalies can contribute in concert to the midlatitude Asian circulation changes and the NEC summer temperature anomalies. These effects overcome those of the central and eastern equatorial Pacific SST anomalies, leading to a same-sign relationship between the NEC summer temperature and the central and eastern equatorial Pacific SST anomalies. Copyright © 2010 by the American Geophysical Union.

Liu S.,Institute of Meteorological science of Jilin Province | Yang S.,National Oceanic and Atmospheric Administration | Lian Y.,Institute of Meteorological science of Jilin Province | Zheng D.,Chinese Academy of Sciences | And 5 more authors.
Journal of Climate | Year: 2010

The time-frequency characteristics of the variations of temperature and precipitation over the city of Changchun in northeast China and their associations with large-scale atmospheric and oceanic conditions are analyzed. It is found that the variations of the regional climate are characterized by strong semiannual signals. For precipitation, the amplitude of semiannual signal is about half of that of the annual cycle. The relationships of the Changchun temperature and precipitation with local winds and large-scale patterns of atmospheric circulation and sea surface temperature are also strongest on annual and semiannual time scales. These strong semiannual signals are potentially helpful for improving the prediction of the regional climate. On the annual time scale, the northeast China climate is affected by both the thermal contrast between the Asian continent and the tropical Indo-Pacific Oceans and that between the continent and the extratropical North Pacific. These effects are manifested by the cyclonic (anticyclonic) pattern over the Asian continent (North Pacific) and the strong southerly flow over East Asia and northwestern Pacific associated with increases in temperature and precipitation. On the semiannual time scale, the northeast China climate is mainly related to the large-scale circulation pattern centered over the North Pacific, with its western portion over northeast China, North and South Korea, and Japan. While temperature signals are related to extratropical atmospheric process more apparently, both extratropical and tropical influences are seen in the semiannual variation of precipitation. There exist strong relationships between Changchun temperature and precipitation and the North Pacific Oscillation (NPO) in the frequency band up to 7 months. Temperature increases and precipitation decreases when NPO is positive. The relationships were weak before 1980 but became stronger afterward, associated with the strengthening of the East Asian trough. © 2010 American Meteorological Society.

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.

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