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Effects of an Urban Park and Residential Area on the atmospheric CO_2 Concentration and Flux in Seoul,Korea

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Advances in atmospheric Sciences 2013年第2期30卷 503-514页

作者： Moon-Soo PARK Seung Jin JOO Chang Seok LEE center for atmospheric and environmental modeling Seoul 151 919Korea Life and environmental Engineering Seoul Women's UniversitySeoul 139 774Korea

The CO2 concentrations and fluxes over an urban forest site （Namsan） and an urban residential region （Boramae） in Seoul, Korea, during the non-growing season （2 4 March 2011）, the growing season （10-12 June 2011）, and the late-growing season （22-24 September 2011） were analyzed. The CO2 concentrations of two sites showed nearly the same diurnal variation, with a maximum value occurring during the night and a minimum value occurring during daytime, as well as the same seasonal variation, with a maximum value during the non-growing season （early spring） and a minimum value during the growing season （summer）. The CO2 flux over the urban forest did not show any typical diurnal variation during the non-growing season, but did show diurnal variation with a small positive value during the night and a large negative value during daytime in the growing and late-growing seasons due to photosynthesis in the urban forest. The CO2 flux over the urban residential region showed a positive daily mean value for all periods, with large values during the non-growing season and small values during the growing season, and it also showed diurnal variation with two maxima at 0600-1000 LST and 1800-2400 LST, and two minima at 0300-0600 LST and 1100-1500 LST, and was strongly correlated with the use of liquefied natural gas for cooking and heating by surrounding houses.

关键词： C02 concentration C02 flux Seoul urban forest urban residential region

The Effects of Land Surface Process Perturbations in a Global Ensemble Forecast System

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Advances in atmospheric Sciences 2016年第10期33卷 1199-1208页

作者： Guo DENG Yuejian ZHU Jiandong GONG Dehui CHEN Richard WOBUS Zhe ZHANG National Meteorological center China Meteorological Administration environmental modeling center National Centers for Environmental Prediction5830 University Research Court Institute of atmospheric Physics Chinese Academy of Sciences

atmospheric variability is driven not only by internal dynamics, but also by external forcing, such as soil states, SST, snow, sea-ice cover, and so on. To investigate the forecast uncertainties and effects of land surface processes on numerical weather prediction, we added modules to perturb soil moisture and soil temperature into NCEP＇s Global Ensemble Forecast System （GEFS）, and compared the results of a set of experiments involving different configurations of land surface and atmospheric perturbation. It was found that uncertainties in different soil layers varied due to the multiple timescales of interactions between land surface and atmospheric processes. Perturbations of the soil moisture and soil temperature at the land surface changed sensible and latent heat flux obviously, as compared to the less or indirect land surface perturbation experiment from the day-to-day forecasts. Soil state perturbations led to greater variation in surface heat fluxes that transferred to the upper troposphere, thus reflecting interactions and the response to atmospheric external forcing. Various verification scores were calculated in this study. The results indicated that taking the uncertainties of land surface processes into account in GEFS could contribute a slight improvement in forecast skill in terms of resolution and reliability, a noticeable reduction in forecast error, as well as an increase in ensemble spread in an under-dispersive system. This paper provides a preliminary evaluation of the effects of land surface processes on predictability. Further research using more complex and suitable methods is needed to fully explore our understanding in this area.

关键词： perturbation land surface processes GEFS ensemble transform with rescaling

Improving Multi-model Ensemble Probabilistic Prediction of Yangtze River Valley Summer Rainfall

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Advances in atmospheric Sciences 2015年第4期32卷 497-504页

作者： LI Fang LIN Zhongda International center for Climate and environmental Sciences Institute of Atmospheric PhysicsChinese Academy of Sciences State Key Laboratory of Numerical modeling for atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences

Seasonal prediction of summer rainfall over the Yangtze River valley（YRV） is valuable for agricultural and industrial production and freshwater resource management in China, but remains a major challenge. Earlier multi-model ensemble（MME） prediction schemes for summer rainfall over China focus on single-value prediction, which cannot provide the necessary uncertainty information, while commonly-used ensemble schemes for probability density function（PDF） prediction are not adapted to YRV summer rainfall prediction. In the present study, an MME PDF prediction scheme is proposed based on the ENSEMBLES hindcasts. It is similar to the earlier Bayesian ensemble prediction scheme, but with optimization of ensemble members and a revision of the variance modeling of the likelihood function. The optimized ensemble members are regressed YRV summer rainfall with factors selected from model outputs of synchronous 500-h Pa geopotential height as predictors. The revised variance modeling of the likelihood function is a simple linear regression with ensemble spread as the predictor. The cross-validation skill of 1960–2002 YRV summer rainfall prediction shows that the new scheme produces a skillful PDF prediction, and is much better-calibrated, sharper, and more accurate than the earlier Bayesian ensemble and raw ensemble.

关键词： probability density function seasonal prediction multi-model ensemble Yangtze River valley summer rainfall Bayesian scheme

Influence of a Southern Shift of the ITCZ from Quick Scatterometer Data on the Pacific North Equatorial Countercurrent

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Advances in atmospheric Sciences 2012年第6期29卷 1292-1304页

作者：吴方华林鹏飞刘海龙 Division of Climate System modeling National Climate Center State Key of Laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences State Key Laboratory of Numerical modeling for atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences

By analyzing the climatologically averaged wind stress during 2000-2007, it is found that the easterly wind stress in the northern tropical Pacific Ocean from Quick Scatterometer （QSCAT） data was stronger than those from Tropical Atmosphere Ocean （TAO） data and from National centers for environmental Prediction/National center for atmospheric Research （NCEP/NCAR） reanalysis I. As a result, the Intertropical Convergence Zone （ITCZ） in the Pacific Ocean is more southward in the QSCAT data than in the NCEP/NCAR data. Relative to the NCEP wind led to negative anomaly of wind stress curl north of the southern shift of the ITCZ in the QSCAT data a latitude of 6°N. The negative anomaly results in downward Ekman pumping in the central Pacific. The excessive local strong easterly wind also contributes to the downward Ekman pumping. This downward Ekman pumping suppresses the thermocline ridge, reduces the meridional thermocline slope and weakens the North Equatorial Countereurrent （NECC）. These effects were confirmed by numerical experiments using two independent ocean general circulation models （OGCMs）. Furthermore, the excessive equatorial easterly wind stress was also found to contribute to the weaker NECC in the OGCMs. A comparison between the simulations and observation data indicates that the stronger zonal wind stress and its southern shift of QSCAT data in the ITCZ region yield the maximum strength of the simulated NECC only 33% of the magnitude derived from observation data and even led to a ＂missing＂ NECC in the western Pacific.

关键词： QuikSCAT wind stress NECC ocean model ITCZ

Coupling and feedback between iron and sulphur in air-sea exchange

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Chinese Science Bulletin 2003年第11期48卷 1080-1086页

作者： ZHUANG Guoshun GUO Jinghua YUAN Hui ZHANG Xingying The center for atmospheric environmental Study Beijing Normal UniversityThe Center for Atmospheric Environmental Study Beijing Normal UniversityThe Center for Atmospheric Environmental Study Beijing Normal UniversityThe Center for Atmospheric Environmental Study Beijing Normal University Beijing 100875 China Beijing 100875 China Beijing 100875 China Beijing 100875 China

Iron in surface seawater has been demonstrated to be the limiting nutrient factor for primary productivity in certain oceanic regions. In 1992 we reported inNature at first Fe(II) existence in marine aerosols over the remote Pacific and Atlantic and proposed the hypothesis of coupling and feedback between iron and sulfur in air-sea exchange. We recently detected a considerable amount of Fe(II) in the aerosols collected during dust storm in Beijing. The concentration of Fe(II) in the dust storm was as high as 1.8–4.3 g · m?3 that accounted for 1.4% –2.6% of the total Fe mass concentration in aerosols, while Fe(II) in the aerosols collected from non-dust storm days was 0.7% of the total Fe. Fe and S concentrations in the dust storm aerosol samples represent a very positive correlationship. The size distribution of Fe, Fe(II), and S in either dust storm particles or the normal aerosols showed the same peak at 1–3 μm. The oxidation of S(IV) under natural light and UV in addition of Fe(III) was 6.5 and 14 times faster respectively compared with that of non-addition. The photoreduction of Fe(□) to Fe(II), through the formation of an OH radical, associated with the oxidation of S(IV) to S(VI) could account for ～3%–20% of the formation of non-sea salt sulfate aerosols at Midway, central Pacific. These results further support the Fe-S coupling hypothesis. From consideration of both the marine biological production of dimethylsulphide (DMS) and the subsequent oxidation of reduced forms of sulfur in the atmosphere, the iron and sulphur cycles in both the atmosphere and the ocean may be closely coupled.

关键词：铁元素海空交换沙尘暴硫元素氧化硫气溶胶海洋天气

Ensemble Forecast: A New Approach to Uncertainty and Predictability

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Advances in atmospheric Sciences 2005年第6期22卷 781-788页

作者： Yuejian ZHU environmental modeling center NCEP/NWS/NOAA Washington DC USA

Ensemble techniques have been used to generate daily numerical weather forecasts since the 1990s in numerical centers around the world due to the increase in computation ability. One of the main purposes of numerical ensemble forecasts is to try to assimilate the initial uncertainty （initial error） and the forecast uncertainty （forecast error） by applying either the initial perturbation method or the multi-model/multiphysics method. In fact, the mean of an ensemble forecast offers a better forecast than a deterministic （or control） forecast after a short lead time （3-5 days） for global modelling applications. There is about a 1-2-day improvement in the forecast skill when using an ensemble mean instead of a single forecast for longer lead-time. The skillful forecast （65% and above of an anomaly correlation） could be extended to 8 days （or longer） by present-day ensemble forecast systems. Furthermore, ensemble forecasts can deliver a probabilistic forecast to the users, which is based on the probability density function （PDF） instead of a single-value forecast from a traditional deterministic system. It has long been recognized that the ensemble forecast not only improves our weather forecast predictability but also offers a remarkable forecast for the future uncertainty, such as the relative measure of predictability （RMOP） and probabilistic quantitative precipitation forecast （PQPF）. Not surprisingly, the success of the ensemble forecast and its wide application greatly increase the confidence of model developers and research communities.

关键词： ensemble forecast predictability uncertainty

Reducing the biases in shortwave cloud radiative forcing in tropical and subtropical regions from the perspective of boundary layer processes

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Science China Earth Sciences 2016年第7期59卷 1427-1439页

作者： SUN Wen Qi LI Li Juan WANG Bin State Key Laboratory of Numerical modeling for atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences Ministry of Education Key Laboratory for Earth System modeling Center of Earth System Science Tsinghua University

Biases in shortwave cloud radiative forcing(SWCF), which cause overestimates in tropical regions and underestimates in subtropical marine stratocumulus regions, are common in many climate models. Here, two boundary layer processes are investigated in the atmospheric model GAMIL2, entrainment at the top of the boundary layer and longwave radiative cooling at the top of stratocumulus clouds, in order to reduce biases and reveal the mechanisms underlying these processes. Our results show that including the entrainment process in the model can reduce negative SWCF biases in most tropical regions but increases positive SWCF biases in subtropical marine stratocumulus regions. This occurs because entrainment reduces the low-level cloud fraction and its cloud liquid water content by suppressing the vertical turbulent diffusion in the boundary layer and decreasing the relative humidity when warm and dry free atmosphere is entrained in the boundary layer. Longwave radiative cooling at the top of stratocumulus clouds can enhance turbulent diffusion within the stratocumulus-topped boundary layer. When combined with the entrainment process, longwave radiative cooling reduces the positive SWCF biases in subtropical marine stratocumulus regions that are observed using the entrainment process alone. The incorporation of these two boundary layer processes improves the simulated SWCF in tropical and subtropical regions in GAMIL2.

关键词： SWCF GAMIL2 Boundary layer Entrainment Stratocumulus

modeling study of source contributions and emergency control effects during a severe haze episode over the Beijing-Tianjin-Hebei area

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Science China Chemistry 2015年第9期58卷 1403-1415页

作者： Huansheng Chen Jie Li Baozhu Ge Wenyi Yang Zifa Wang Si Huang Yuanlin Wang Pingzhong Yan Jianjun Li Lili Zhu State Key Laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry (LAPC) Institute of atmospheric Physics Chinese Academy of Sciences China National environmental Monitoring center

In February 2014, the Beijing-Tianjin-Hebei(BTH) area experienced a weeklong episode of heavy haze pollution. Cities such as Beijing(BJ) and Shijiazhuang(SJZ) issued heavy pollution alerts for the first time and took emergency control measures. This study employed the Nested Air Quality Prediction modeling System(NAQPMS) to simulate and analyze the three-dimensional structure of the source contributions of PM2.5 in the BTH area during this pollution episode and quantitatively assessed the effects of the emergency control measures. The results showed that during the polluted period(February 19–26), surface PM2.5 mainly originated from local sources(48%–72%). In the entire BTH area, southern Hebei(SHB) represented the largest internal contribution(33%), while the main external contributions came from Shandong(SD)(10%) and Henan(HN)(4%). Vertically, the local contribution was constrained below the near-ground layer, and rapidly decreased with altitude. The regional transport path from SHB and Shanxi(SX) to BJ appeared at 0.5–1.5 and 1.5–2.5 km, with contributions of 32%–42% and 13%–27%, respectively. The non-local source regions for the BTH area were SD below 1 km and mainly SX and HN above 1 km. Compared to the non-polluted period(February 27–28), the contribution from regional transport increased during the polluted period, indicating the key role of regional transport in the pollution formation. The emergency control measures had a relatively large effect on NOx and SO2 concentrations, but a limited effect on PM2.5. The stronger regional transport during the polluted period may have weakened the effects of the local emergency control measures. These results indicated that a coordinated emission control should be implemented not only over the BTH area but also over its surrounding provinces(e.g. SD, HN).

关键词： NAQPMS Beijing-Tianjin-Hebei(BTH) source contribution emergency control severe haze PM2.5

Incorporating Groundwater Dynamics and Surface/Subsurface Runoff Mechanisms in Regional Climate modeling over River Basins in China

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Advances in atmospheric Sciences 2013年第4期30卷 983-996页

作者：秦佩华谢正辉袁星 State Key Laboratory of Numerical modeling for atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Department of Civil and environmental Engineering Princeton University

To improve the capability of numerical modeling of climate-groundwater interactions, a groundwater component and new surface/subsurface runoff schemes were incorporated into the regional climate model RegCM3, renamed RegCM3_Hydro. 20-year simulations from both models were used to investigate the effects of groundwater dynamics and surface/subsurface runoff parameterizations on regional climate over seven river basins in China. A comparison of results shows that RegCM3_Hydro reduced the positive biases of annual and summer （June, July, August） precipitation over six river basins, while it slightly increased the bias over the Huaihe River Basin in eastern China. RegCM3_Hydro also reduced the cold bias of surface air temperature from RegCM3 across years, especially for the Haihe and the Huaihe river basins, with significant bias reductions of 0.80~C and 0.88~C, respectively. The spatial distribution and seasonal variations of water table depth were also well captured. With the new surface and subsurface runoff schemes, RegCM3_Hydro increased annual surface runoff by 0.11 0.62 mm d 1 over the seven basins. Though previous studies found that incorporating a groundwater component tends to increase soil moisture due to the consideration of upward groundwater recharge, our present work shows that the modified runoff schemes cause less infiltration, which outweigh the recharge from groundwater and result in drier soil, and consequently cause less latent heat and more sensible heat over most of the basins.

关键词： groundwater runoff river basin regional climate