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Impact of UV-A Radiation on Erythemal UV and UV-index Estimation over Korea

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Advances in atmospheric Sciences 2015年第12期32卷 1639-1646页

作者： Sang Seo PARK Yun Gon LEE Jung Hyun KIM department of atmospheric Sciences Yonsei University department of atmospheric Sciences Chungnam National University

Because total UV （TUV） in the UV-A region is 100 times higher than in the UV-B region, UV-A is a considerable compo- nent when calculating erythemal UV （EUV） and UV-index. The ratio of EUV to TUV in the UV-A value [EUV（A）/TUV（A）] is investigated to convert the EUV（A） from TUV（A） for broadband observation. The representative value of EUV（A）/TUV（A）, from the simulation study, is 6.9 × 10^- 4 changing from 6.1 ×10^-4 to 7.0 × 10^ -4 as aerosol optical depth, total ozone and solar zenith angle change. By adopting the observational data of EUV（B） and TUV（A） from UV-biometer measurements at Yonsei University [（37.57°N, 126.95°E）, 84 m above sea level], the EUV irradiance increases to 15% of EUV（B） due to the consideration of EUV（A） from the data of TUV（A） observation. Compared to the total EUV observed from the Brewer spec- trophotometer at the same site, the EUV（B） from the UV-biometer observes only 95% of total EUV, and its underestimation is caused by neglecting the effect of UV-A. However, the sum of EUV（B） and EUV（A） [EUV（A＋B）] from two UV-biometers is 10% larger than the EUV from the Brewer spectrophotometer because of the spectral overlap effect in the range 320-340 nm. The correction factor for the overlap effect adjusts 8% of total EUV.

关键词： erythemal UV total UV UV-B UV-biometer

A Modeling Study of the Climate Effects of Sulfate and Carbonaceous Aerosols over China

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Advances in atmospheric Sciences 2010年第6期27卷 1276-1288页

作者：刘红年张力吴涧 School of atmospheric Science Nanjing University department of atmospheric Science Yunnan University

In this paper, the RIEMS 2.0 model is used to simulate the distribution of sulfate, black carbon, and organic carbon aerosols over China （16.2°-44.1°N, 93.4°-132.4°E） in 1998. The climate effects of these three anthropogenic aerosols are also simulated. The results are summarized as follows：（1） The regional average column burdens of sulfate, BC, OC, and SOC were 5.9, 0.24, 2.4, and 0.49 mg m-2, with maxima of 33.9, 1.48, 7.3, and 1.1 mg m-2, respectively. The column burden and surface concentration of secondary organic carbon accounted for about 20% and 7%, respectively, of the total organic carbon in eastern China. （2） The radiative forcings of sulfate, organic carbon, and black carbon at the top of the atmosphere were -1.24, -0.6, and 0.16 W m 2 respectively, with extremes of -5.25, -2.6, and 0.91 W m-2. （3） The surface air temperature changes caused by sulfate, organic carbon, and black carbon were -0.07, -0.04, and 0.01 K, respectively. The air temperature increase caused by black carbon at 850 hPa was higher than that at the surface. The net effect of the three kinds of anthropogenic aerosols together decreased the annual average temperature by -0.075 K; the maximum value was -0.3 K. （4） Black carbon can reduce the precipitation in arid and semi-arid areas of northern China and increase the precipitation in wet and semi-wet areas of southern China. The average precipitation increase caused by black carbon in China was 0.003 mm d^-1. The net effect of the three kinds of anthropogenic aerosols was to decrease the precipitation over China by 0.008 mmd ^-1.

关键词： black carbon organic carbon sulfate aerosol climate effect RIEMS2.0

Impacts of Soil Moisture on the Numerical Simulation of a Post-Landfall Storm

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Journal of Meteorological Research 2019年第2期33卷 206-218页

作者： Feimin ZHANG Zhaoxia PU Chenghai WANG College of atmospheric Sciences Lanzhou University department of atmospheric Sciences University of Utah

Surface heat and moisture fluxes are important to the evolution of a tropical storm after its landfall. Soil moisture is one of the essential components that influence surface heating and moisture fluxes. In this study, the impact of soil moisture on a pre-landfall numerical simulation of Tropical Storm Bill(2015), which had a much longer lifespan over land, is investigated by using the research version of the NCEP Hurricane Weather Research and Forecasting(HWRF) model. It is found that increased soil moisture with SLAB scheme before storm's landfall tends to produce a weaker storm after landfall and has negative impacts on storm track simulation. Further diagnoses with different land surface schemes and sensitivity experiments indicate that the increase in soil moisture inside the storm corresponds to a strengthened vertical mixing within the storm boundary layer, which is conducive to the decay of storm and has negative impacts on storm evolution. In addition, surface diabatic heating effects over the storm environment are also found to be an important positive contribution to the storm evolution over land, but their impacts are not so substantial as boundary layer vertical mixing inside the storm. The overall results highlight the importance and uncertainty of soil moisture in numerical model simulations of landfalling hurricanes and their further evolution over land.

关键词： soil moisture tropical storm tropical cyclone landfall la nd surface numerical simulation

New findings on the influence of El Nino events on tropical cyclone formation

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Science China Earth Sciences 2024年第3期67卷 892-893页

作者： Liguang WU department of atmospheric and Oceanic Sciences Institute of Atmospheric SciencesFudan UniversityShanghai 200438China

Tropical cyclones typically form over warm tropical and subtropical ocean surfaces, as their formation and intensification rely primarily on the energy provided by the ocean. Pioneering research by Gray (1968) revealed that the formation of tropical cyclones requires the sea surface temperature (SST) to be no less than 26.5℃. Consequently, SST is commonly recognized as a crucial parameter among the environmental factors influencing tropical cyclone formation(Gray, 1979;Emanuel and Nolan, 2004).

关键词： tropical cyclone ocean

Possible Impacts of the Arctic Oscillation on the Interdecadal Variation of Summer Monsoon Rainfall in East Asia

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Advances in atmospheric Sciences 2005年第1期22卷 39-48页

作者：琚建华吕俊梅曹杰任菊章 China Meteorological Administration Training Centre Institute of atmospheric Physics department of atmospheric Sciences

The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the variation of the AO index and the leading principal component time series of the summer rainfall in East Asia. The rainfall anomaly changed from below normal to above normal in central China, the southern part of northeastern China and the Korean peninsula around 1978. However, the opposite interdecadal variation was found in the rainfall anomaly in North China and South China. The interdecadal variation of summer rainfall is associated with the weakening of the East Asia summer monsoon circulation. It is indicated that the interdecadal variation of the AO exerts an influence on the weakening of the monsoon circulation. The recent trend in the AO toward its high-index polarity during the past two decades plays important roles in the land-sea contrast anomalies and wintertime precipitation anomaly. The mid- and high-latitude regions of the Asian continent are warming, while the low-latitude regions are cooling in winter and spring along with the AO entering its high-index polarity after the late 1970s. In the meantime, the precipitation over the Tibetan Plateau and South China is excessive, implying an increase of soil moisture. The cooling tendency of the land in the southern part of Asia will persist until summer because of the memory of soil moisture. So the warming of the Asian continent is relatively slow in summer. Moreover, the Indian Ocean and Pacific Ocean, which are located southward and eastward of the Asian land, are warming from winter to summer. This suggests that the contrast between the land and sea is decreased in summer. The interdecadal decrease of the land-sea heat contrast finally leads to the weakening of the East Asia summer monsoon circulation.

关键词： the Arctic Oscillation interdecadal variation summer monsoon rainfall land-sea heat contrast

Ensemble-based Kalman Filters in Strongly Nonlinear Dynamics

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Advances in atmospheric Sciences 2009年第3期26卷 373-380页

作者： Zhaoxia PU Joshua HACKER department of atmospheric Sciences University of Utah USA National Center for atmospheric Research USA

This study examines the effectiveness of ensemble Kalman filters in data assimilation with the strongly nonlinear dynamics of the Lorenz-63 model, and in particular their use in predicting the regime transition that occurs when the model jumps from one basin of attraction to the other. Four configurations of the ensemble-based Kalman filtering data assimilation techniques, including the ensemble Kalman filter, en- semble adjustment Kalman filter, ensemble square root filter and ensemble transform Kalman filter, are evaluated with their ability in predicting the regime transition （also called phase transition） and also are compared in terms of their sensitivity to both observational and sampling errors. The sensitivity of each ensemble-based filter to the size of the ensemble is also examined.

关键词： ensemble Kalman filter nonlinear data assimilation Lorenz model

Gustiness and Coherent Structure of Strong Winds and Their Role in Dust Emission and Entrainment

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Advances in atmospheric Sciences 2010年第1期27卷 1-13页

作者：曾庆存程雪玲胡非彭珍 Institute of atmospheric Physics Chinese Academy of Sciences department of atmospheric Science Nanjing University

After the passage of a cold front, spring in northern China, the outbreak of strong wind is often accompanied by dust emissions. Through analyses of data in the atmospheric boundary layer during a typical case, it is revealed there are rather regular gust wave packets superimposed on the basic strong wind flow. The gust-wind wave packets have a period equal to around 3 6 rains and possess coherent structure. As the vertical transport of momentum is decomposed into separate parts by （a） basic flow, （b） gust-wind, and （c） turbulence, they are all in a downwards direction at the lower levels of the atmospheric boundary layer during strong wind periods. However, （a） is the largest, while （b） and （c） are comparable. All these are very different from the case of normal weather. Besides, the friction velocity at the ground surface is also much larger than that of normal weather and should be corrected by taking the contributions of the basic flow and gust-wind into *** strong basic flow with descending motion is very favorable for soil erosion and sand/dust emissions, but suppresses the entrainment of dust particles by keeping them within the bottom levels of the atmospheric boundary layer. Owing to the coherent structure of gust-wind, dust particles can effectively overcome the systematic descending air motion and penetrate into the middle and upper levels of the atmospheric boundary layer, and then propagate further and diffuse into the troposphere where ascending air motion prevails.

关键词： gust-wind coherent structure descending motion dust storm soil erosion dust entrainment

Impacts of Coastal SST Variability on the East Asian Summer Monsoon

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Advances in atmospheric Sciences 2007年第2期24卷 259-270页

作者：黄安宁张耀存高新房 department of atmospheric Sciences Nanjing University

The impacts of the seasonal and interannual SST variability in the East Asia coastal regions （EACRSST） on the East Asian summer monsoon （EASM） have been examined using a regional climate model （PδRCM9） in this paper. The simulation results show that the correlation between the EACRSST and the EASM is strengthened after the mid-1970s and also the variability of the EACRSST forcing becomes much more important to the EASM interannual variability after the mid-1970s. The impacts of the EACRSST on the summer precipitation over each sub-region in the EASM region become weak gradually from south to north, and the temporal evolution features of the summer precipitation differences over North and Northeast China agree well with those of the index of EASM （IEASM） differences. The mechanism analyses show that different EACRSST forcings result in the differences of sensible and latent heat flux exchanges at the air-sea interface, which alter the heating rate of the atmosphere. The heating rate differences induce low level air temperature differences over East Asia, resulting in the differences of the land-sea thermal contrast （LSTC） which lead to 850 hPa geopotential height changes. When the 850 hPa geopotential height increases over the East Asian continent and decreases over the coast of East China and the adjacent oceans during the weakening period of weakens consequently. On the contrary, the EASM enhances during the strengthening period of the LSTC.

关键词： SST variability coastal oceans East Asian monsoon numerical simulations

Numerical Simulations of Heavy Rainfall over Central Korea on 21 September 2010 Using the WRF Model

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Advances in atmospheric Sciences 2015年第6期32卷 855-869页

作者： Ui-Yong BYUN Jinkyu HONG Song-You HONG Hyeyum Hailey SHIN department of atmospheric Sciences Yonsei University Korea Institute of atmospheric Prediction Systems NCAR

On 21 September 2010, heavy rainfall with a local maximum of 259 mm d-1 occurred near Seoul, South Korea. We examined the ability of the Weather Research and Forecasting （WRF） model in reproducing this disastrous rainfall event and identified the role of two physical processes： planetary boundary layer （PBL） and microphysics （MPS） processes. The WRF model was forced by 6-hourly National Centers for Environmental Prediction （NCEP） Final analysis （FNL） data for 36 hours form 1200 UTC 20 to 0000 UTC 22 September 2010. Twenty-five experiments were performed, consisting of five different PBL schemes--Yonsei University （YSU）, Mellor-Yamada-Janjic （MYJ）, Quasi Normal Scale Elimination （QNSE）, Bougeault and Lacarrere （BouLac）, and University of Washington （UW）--and five different MPS schemes--WRF Single- Moment 6-class （WSM6）, Goddard, Thompson, Milbrandt 2-moments, and Morrison 2-moments. As expected, there was a specific combination of MPS and PBL schemes that showed good skill in forecasting the precipitation. However, there was no specific PBL or MPS scheme that outperformed the others in all aspects. The experiments with the UW PBL or Thompson MPS scheme showed a relatively small amount of precipitation. Analyses form the sensitivity experiments confirmed that the spatial distribution of the simulated precipitation was dominated by the PBL processes, whereas the MPS processes determined the amount of rainfall. It was also found that the temporal evolution of the precipitation was influenced more by the PBL processes than by the MPS processes.

关键词： heavy rainfall WRF model microphysics planetary boundary layer