Changes of Dry-wet Climate in the Dry Season in Yunnan(1961-2007)

Factor analysis was used to investigate the changes of dry-wet climate in the dry season in Yunnan during 1961-2007 based on observed data from 15 stations.Three common factors were extracted from the 9 climatic factors.The results showed that the dry-wet climate has evidently changed since the early 1960s.The general trends in the changes of drywet climate were described as slight decrease in humidity and gradual enhancement in drought intensity.The climate during 1960s-1980s was under weak-medium drought.But since early 1990s,dry conditions have markedly strengthened and continued due to uneven temporal distribution of rainfall and climate warming.

Improved EOF-based bias correction method for seasonal forecasts and its application in IAP AGCM4.1

An effective improvement on the empirical orthogonal function(EOF)–based bias correctionmethod for seasonal forecasts is proposed in this paper,by introducing a stepwise regression method into the process of EOF time series correction.Using 30-year(1981–2010)hindcast results from IAP AGCM4.1(the latest version of this model),the improved method is validated for the prediction of summer(June–July–August)rainfall anomalies in Southeast China.The results in terms of the pattern correction coefficient(PCC)of rainfall anomalies shows that the 30-year-averaged prediction skill improves from 0.01 to 0.06 with the original correction method,and to 0.29 using the improved method.The applicability in real-time prediction is also investigated,using 2016 summer rainfall prediction as a test case.With a PCC of 0.59,the authors find that the new correction method significantly improves the prediction skill;the PCC using the direct prediction of the model is?0.04,and using the old bias correction method it is 0.37.

Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.

Subseasonal prediction of winter precipitation in southern China using the early November snowpack over the Urals

Evolution of the autumn snowpack has been considered as a potential source for the subseasonal predictability of winter surface air temperature,but its linkage to precipitation variability has been less well discussed.This study shows that the snow water equivalent(SWE)over the Urals region in early(1–14)November is positively associated with precipitation in southern China during15–21 November and 6–15 January,based on the study period 1979/80–2016/17.In early November,a decreased Urals SWE warms the air locally via diabatic heating,indicative of significant land–atmosphere coupling over the Urals region.Meanwhile,a stationary Rossby wave train originates from the Urals and propagates along the polar-front jet stream.In mid(15–21)November,this Rossby wave train propagates downstream toward East Asia and,combined with the deepened East Asian trough,reduces the precipitation over southern China by lessening the water vapor transport.Thereafter,during 22 November to 5 January,there are barely any obvious circulation anomalies owing to the weak land–atmosphere coupling over the Urals.In early(6–15)January,the snowpack expands southward to the north of the Mediterranean Sea and cools the overlying atmosphere,suggestive of land–atmosphere coupling occurring over western Europe.A stationary Rossby wave train trapped in the subtropical westerly jet stream appears along with anomalous cyclonic circulation over Europe,and again with a deepened East Asian trough and less precipitation over southern China.The current findings have implications for winter precipitation prediction in southern China on the subseasonal timescale.

STATISTICAL CHARACTERISTICS AND NUMERICAL SIMULATION OF SEA-LAND BREEZES IN HAINAN ISLAND

The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze(SLB) is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency(49%) in summer and the minimum frequency(29%) in autumn. SLB frequencies(41%) are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the central mountain exhibits significant impacts on low-level airflow. A windward land breeze front usually occurs along the coastline between the wee hours and the morning in summer, with an arc-shaped convergence zone about 10 to 30 km off shore. In winter the arc-shaped convergence zone is weak and appears only in the southeast coastal area. Landing on the flat regions of northern to western parts of the island and going inland from there, the sea breeze front at the leeward side meets with that at the windward side in the centre of the island when sea breeze fully develops, causing an intense convergence zone throughout the whole island. Consistent with prevailing winds in direction, the windward sea breeze and leeward land breeze develop quickly but are not distinguishable from background winds.

Seasonal Effect on Atmospheric Refractivity in Diverse Terrains

Air masses in the atmosphere have contrasting temperature, humidity and moisture, which influence radio signals traversing the atmosphere. The influence of the atmosphere on refractivity is strongly determined by its temporal and spatial variability. This paper uses meteorological measurements to investigate the impact of meteorological structures on diverse environments evident in Nigeria. The study hypothesises that refractivity measures could serve as indicators of diurnal radio wave degradation traversing the atmosphere.

Improving Fuel Diesel Efficiency Using Fuel Filter

The price of fuel oil continues to rise, decreased supplies oil at the other side, both factors increase the interest of researchers to conduct research related to fuel efficiency. Therefore the aim of this study is to improve the efficiency fuel of diesel engine using fuel filter. The method used for the research is testing the most efficient fuel filters made of coil wire coil winding 5,000, the three distinguished from the coil core diameter of 44.5, 28.5 and 17.5 mm in diesel engine. The performance test was conducted from 1,100 rpm to 1,700 rpm, the throttle opening of 30%-60%. The first testing was done by creating a constant speed 1,500 rpm and throttle opening varies from 30% to 60%, further testing is done by varying the rpm start from 1,100 rpm to 1,700 rpm to make constant valve 40% and 60%.

球面日晷的设计原理

通过各天球坐标的关系以及日晷的投影原理设计出球面日晷,它是赤道式日晷、圭表和现代精密天文测算相结合的产物.日晷测得的时刻为当地真太阳时,根据经度差与时刻差的关系,可在晷面上直接将时刻修正为北京视时,进行均时差校正后得到北京时间.同时通过对太阳周年回归运动的分析,设置节气线,由晷针针尖在晷面投影的节气位置来判断当天所处的日期.

Hydrological monitoring and seasonal forecasting:Progress and perspectives

Hydrological monitoring and seasonal forecasting is an active research field because of its potential applications in hydrological risk assessment, preparedness and mitigation. In recent decades, developments in ground and satellite measurements have made the hydrometeorological information readily available, and advances in information technology have facilitated the data analysis in a real-time manner. New progress in climate research and modeling has enabled the prediction of seasonal climate with reasonable accuracy and increased resolution. These emerging techniques and advances have enabled more timely acquisition of accurate hydrological fluxes and status, and earlier warning of extreme hydrological events such as droughts and floods. This paper gives current state-of-the-art understanding of the uncertainties in hydrological monitoring and forecasting, reviews the efforts and progress in operational hydrological monitoring system assisted by observations from various sources and experimental seasonal hydrological forecasting, and briefly introduces the current monitoring and forecasting practices in China. The grand challenges and perspectives for the near future are also discussed, including acquiring and extracting reliable information for monitoring and forecasting, predicting realistic hydrological fluxes and states in the river basin being significantly altered by human activity, and filling the gap between numerical models and the end user. We highlight the importance of understanding the needs of the operational water management and the priority to transfer research knowledge to decision-makers.