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Publisher: Springer-Verlag (Total: 2352 journals)

 Advances in Atmospheric SciencesJournal Prestige (SJR): 0.956 Citation Impact (citeScore): 2Number of Followers: 37      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1861-9533 - ISSN (Online) 0256-1530 Published by Springer-Verlag  [2352 journals]
• First Rocketsonde Launched from an Unmanned Semi-submersible Vehicle
• Authors: Hongbin Chen; Jun Li; Yuejian Xuan; Xiaosong Huang; Weifeng Zhu; Keping Zhu; Wenzheng Shao
Pages: 339 - 345
Abstract: The unmanned semi-submersible vehicle (USSV) developed by the unmanned surface vehicle team of the Institute of Atmospheric Physics is an unmanned, rugged, and high-endurance autonomous navigation vessel designed for the collection of long-term, continuous and real-time marine meteorological measurements, including atmospheric sounding in the lower troposphere. A series of river and sea trials were conducted from May 2016 to November 2017, and the first rocketsonde was launched from the USSV. Real-time meteorological parameters in the marine atmospheric boundary layer (MABL) were obtained, including sea surface temperature, and vertical profiles of the pressure, temperature, relative humidity, wind speed, and wind direction. These data are extremely useful and important for research on air–sea interactions, sea surface heat and latent heat flux estimations, MABL modeling, and marine satellite product validation.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8249-5
Issue No: Vol. 36, No. 4 (2019)

• Seasonal Variations of Observed Raindrop Size Distribution in East China
• Authors: Long Wen; Kun Zhao; Mengyao Wang; Guifu Zhang
Pages: 346 - 362
Abstract: Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a two-dimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain drop size distribution (DSD) characteristics are revealed for different rain types and seasons. Summer rainfall is dominated by convective rain, while during the other seasons the contribution of stratiform rain to rainfall amount is equal to or even larger than that of convective rain. The mean mass-weighted diameter versus the generalized intercept parameter pairs of convective rain are plotted roughly around the “maritime” cluster, indicating a maritime nature of convective precipitation throughout the year in East China. The localized rainfall estimators, i.e., rainfall kinetic energy–rain rate, shape–slope, and radar reflectivity–rain rate relations are further derived. DSD variability is believed to be a major source of diversity of the aforementioned derived estimators. These newly derived relations would certainly improve the accuracy of rainfall kinetic energy estimation, DSD retrieval, and quantitative precipitation estimation in this specific region.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8107-5
Issue No: Vol. 36, No. 4 (2019)

• Assessment of Temperature Extremes in China Using RegCM4 and WRF
• Authors: Xianghui Kong; Aihui Wang; Xunqiang Bi; Dan Wang
Pages: 363 - 377
Abstract: This study assesses the performance of temperature extremes over China in two regional climate models (RCMs), RegCM4 and WRF, driven by the ECMWF’s 20th century reanalysis. Based on the advice of the Expert Team on Climate Change Detection and Indices (ETCCDI), 12 extreme temperature indices (i.e., TXx, TXn, TNx, TNn, TX90p, TN90p, TX10p, TN10p WSDI, ID, FD, and CSDI) are derived from the simulations of two RCMs and compared with those from the daily station-based observational data for the period 1981–2010. Overall, the two RCMs demonstrate satisfactory capability in representing the spatiotemporal distribution of the extreme indices over most regions. RegCM performs better than WRF in reproducing the mean temperature extremes, especially over the Tibetan Plateau (TP). Moreover, both models capture well the decreasing trends in ID, FD, CSDI, TX10p, and TN10p, and the increasing trends in TXx, TXn, TNx, TNn, WSDI, TX90p, and TN90p, over China. Compared with observation, RegCM tends to underestimate the trends of temperature extremes, while WRF tends to overestimate them over the TP. For instance, the linear trends of TXx over the TP from observation, RegCM, and WRF are 0.53°C (10 yr)−1, 0.44°C (10 yr)−1, and 0.75°C (10 yr)−1, respectively. However, WRF performs better than RegCM in reproducing the interannual variability of the extreme-temperature indices. Our findings are helpful towards improving our understanding of the physical realism of RCMs in terms of different time scales, thus enabling us in future work to address the sources of model biases.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8144-0
Issue No: Vol. 36, No. 4 (2019)

• Interannual Salinity Variability in the Tropical Pacific in CMIP5
Simulations
• Authors: Hai Zhi; Rong-Hua Zhang; Pengfei Lin; Peng Yu
Pages: 378 - 396
Abstract: Salinity variability and its causes in the tropical Pacific are analyzed using observations, reanalysis products and model simulations. The mixed-layer salinity (MLS) budget analyses from observations and reanalysis products indicate that its interannual evolution is closely related to ENSO and is predominantly governed by surface forcing and surface advection in the western-central equatorial Pacific. It is found that the observed MLS tendency leads Ni˜no3.4 by about 12 months due to the effect of negative freshwater flux (evaporation minus precipitation). These observation-based analyses are used to evaluate the corresponding simulation using GFDL-ESM2M. It is evident that the model can simulate the spatiotemporal variations of MLS with some discrepancies compared to observations. In the warm pool of the equatorial Pacific the MLS tendency in the model is sensitive to ocean dynamics, however model biases cause the tendency to be underestimated. In particular, the freshwater flux is overestimated while the ocean surface zonal current and vertical velocity at the base of the mixed layer are underestimated. Due to model biases in representing the related physics, the effects of surface forcing on the simulated MLS budget are overestimated and those of subsurface and surface advection are relatively weak. Due to weaker surface advection and subsurface forcing than observed, the simulated compensations for surface forcing are suppressed, and the simulated MLS tendency that leads Ni˜no3.4 by 8–10 months, which is shorter than the observed lead time. These results are useful for the interpretation of observational analyses and other model simulations in the tropical Pacific.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-7309-1
Issue No: Vol. 36, No. 4 (2019)

• Errors in Current Velocity in the Low-latitude North Pacific: Results from
the Regional Ocean Modeling System
• Authors: Xixi Wen; Wansuo Duan
Pages: 397 - 416
Abstract: Using the Regional Ocean Modeling System, this study investigates the simulation uncertainties in the current velocity in the low-latitude North Pacific where the Kuroshio originates [i.e., the beginning of the Kuroshio (BK)]. The results show that the simulation uncertainties largely reflect the contributions of wind stress forcing errors, especially zonal wind stress errors, rather than initial or boundary errors. Using the idea of a nonlinear forcing singular vector, two types of zonal wind stress errors (but sharing one EOF mode) are identified from error samples derived from reanalysis data as having the potential to yield large simulation uncertainties. The type-1 error possesses a pattern with positive anomalies covering the two zonal bands of 0°–15°N and 25°–40°N in the Pacific Ocean, with negative anomalies appearing between these two bands; while the type-2 error is almost opposite to the type-1 error. The simulation uncertainties induced by the type-1 and −2 errors consist of both large-scale circulation errors controlled by a mechanism similar to the Sverdrup relation and mesoscale eddy-like errors generated by baroclinic instability. The type-1 and −2 errors suggest two areas: one is located between the western boundary and the meridional 130°E along 15°–20°N, and the other is located between 140°–150°E and along 15°–20°N. The reduction of errors over these two areas can greatly improve the simulation accuracy of the current velocity at BK. These two areas represent sensitive areas for targeted observations associated with the simulation of the current velocity at BK.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8140-4
Issue No: Vol. 36, No. 4 (2019)

• Intraseasonal Oscillation of Tropospheric Ozone over the Indian Summer
Monsoon Region
• Authors: Yuli Zhang; Chuanxi Liu; Yi Liu; Rui Yang
Pages: 417 - 430
Abstract: Boreal summer intraseasonal oscillation (BSISO) of lower tropospheric ozone is observed in the Indian summer monsoon (ISM) region on the basis of ERA-Interim reanalysis data and ozonesonde data from the World Ozone and Ultraviolet Radiation Data Centre. The 30–60-day intraseasonal variation of lower-tropospheric ozone shows a northwest–southeast pattern with northeastward propagation in the ISM region. The most significant ozone variations are observed in the Maritime Continent and western North Pacific. In the tropics, ozone anomalies extend from the surface to 300 hPa; however, in extratropical areas, it is mainly observed under 500 hPa. Precipitation caused by BSISO plays a dominant role in modulating the BSISO of lower-tropospheric ozone in the tropics, causing negative/positive ozone anomalies in phases 1–3/5–6. As the BSISO propagates northeastward to the western North Pacific, horizontal transport becomes relatively more important, increasing/reducing tropospheric ozone via anticyclonic/cyclonic anomalies over the western North Pacific in phases 3–4/7–8. As two extreme conditions of the ISM, most of its active/break events occur in BSISO phases 4–7/1–8 when suppressed/enhanced convection appears over the equatorial eastern Indian Ocean and enhanced/suppressed convection appears over India, the Bay of Bengal, and the South China Sea. As a result, the BSISO of tropospheric ozone shows significant positive/negative anomalies over the Maritime Continent, as well as negative/positive anomalies over India, the Bay of Bengal, and the South China Sea in active/break spells of the ISM. This BSISO of tropospheric ozone is more remarkable in break spells than in active spells of the ISM, due to the stronger amplitude of BSISO in the former.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8113-7
Issue No: Vol. 36, No. 4 (2019)

• Numerical Study of Boundary Layer Structure and Rainfall after Landfall of
Typhoon Fitow (2013): Sensitivity to Planetary Boundary Layer
Parameterization
• Authors: Meiying Dong; Chunxiao Ji; Feng Chen; Yuqing Wang
Pages: 431 - 450
Abstract: The boundary layer structure and related heavy rainfall of Typhoon Fitow (2013), which made landfall in Zhejiang Province, China, are studied using the Advanced Research version of the Weather Research and Forecasting model, with a focus on the sensitivity of the simulation to the planetary boundary layer parameterization. Two groups of experiments—one with the same surface layer scheme and including the Yonsei University (YSU), Mellor–Yamada–Nakanishi–Niino Level 2.5, and Bougeault and Lacarrere schemes; and the other with different surface layer schemes and including the Mellor–Yamada–Janjić and Quasi-Normal Scale Elimination schemes—are investigated. For the convenience of comparative analysis, the simulation with the YSU scheme is chosen as the control run because this scheme successfully reproduces the track, intensity and rainfall as a whole. The maximum deviations in the peak tangential and peak radial winds may account for 11% and 33% of those produced in the control run, respectively. Further diagnosis indicates that the vertical diffusivity is much larger in the first group, resulting in weaker vertical shear of the tangential and radial winds in the boundary layer and a deeper inflow layer therein. The precipitation discrepancies are related to the simulated track deflection and the differences in the simulated low-level convergent flow among all tests. Furthermore, the first group more efficiently transfers moisture and energy and produces a stronger ascending motion than the second, contributing to a deeper moist layer, stronger convection and greater precipitation.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-7281-9
Issue No: Vol. 36, No. 4 (2019)

• Surface Rainfall Processes during the Genesis Period of Tropical Cyclone
Durian (2001)
• Authors: Yaping Wang; Yongjie Huang; Xiaopeng Cui
Pages: 451 - 464
Abstract: The rainfall processes during the formation of tropical cyclone (TC) Durian (2001) were investigated quantitatively using the three-dimensional (3D) WRF-based precipitation equation. The rain rate (PS) decreased slightly as the TC approached to formation, and then increased as Durian began to intensify. The rate of moisture-related processes (QWV) in the equation contributed around 80% to PS before TC genesis, and made more contribution during and after TC genesis. The rate of hydrometeor-related processes (QCM) contributed about 20% before TC formation, followed by less contribution during and after TC formation. QWV were dominated by the 3D moisture flux advection rate (QWVA), while the surface evaporation rate (QWVE) also played an important role. Just before TC genesis, moisture from QWVA and QWVE helped the local atmosphere moisten (negative QWVL). QCM were determined by the 3D hydrometeor advection rates (QCLA and QCIA) and the local change rates of hydrometeors (QCLL and QCIL). During TC formation, QCM largely decreased and then reactivated as Durian began to intensify, accompanied by the development of TC cloud. Both the height and the strength of the net latent heating center associated with microphysical processes generally lowered before and during TC genesis, resulting mainly from lessening deposition and condensation. The downward shift of the net latent heating center induced a more bottom-heavy upward mass flux profile, suggesting to promote lower-tropospheric convergence in a shallower layer, vorticity amplification and TC spin-up.
PubDate: 2019-04-01
DOI: 10.1007/s00376-018-8157-8
Issue No: Vol. 36, No. 4 (2019)

• 2018 Continues Record Global Ocean Warming
• Authors: Lijing Cheng; Jiang Zhu; John Abraham; Kevin E. Trenberth; John T. Fasullo; Bin Zhang; Fujiang Yu; Liying Wan; Xingrong Chen; Xiangzhou Song
Pages: 249 - 252
PubDate: 2019-03-01
DOI: 10.1007/s00376-019-8276-x
Issue No: Vol. 36, No. 3 (2019)

• Predictability of South China Sea Summer Monsoon Onset
• Authors: Gill M. Martin; Amulya Chevuturi; Ruth E. Comer; Nick J. Dunstone; Adam A. Scaife; Daquan Zhang
Pages: 253 - 260
Abstract: Predicting monsoon onset is crucial for agriculture and socioeconomic planning in countries where millions rely on the timely arrival of monsoon rains for their livelihoods. In this study we demonstrate useful skill in predicting year-to-year variations in South China Sea summer monsoon onset at up to a three-month lead time using the GloSea5 seasonal forecasting system. The main source of predictability comes from skillful prediction of Pacific sea surface temperatures associated with El Niño and La Niña. The South China Sea summer monsoon onset is a known indicator of the broadscale seasonal transition that represents the first stage of the onset of the Asian summer monsoon as a whole. Subsequent development of rainfall across East Asia is influenced by subseasonal variability and synoptic events that reduce predictability, but interannual variability in the broadscale monsoon onset for East Asian summer monsoon still provides potentially useful information for users about possible delays or early occurrence of the onset of rainfall over East Asia.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8100-z
Issue No: Vol. 36, No. 3 (2019)

• Seesaw Pattern of Rainfall Anomalies between the Tropical Western North
Pacific and Central Southern China during Late Summer
• Authors: Xinyu Li; Riyu Lu
Pages: 261 - 270
Abstract: It is well known that suppressed convection in the tropical western North Pacific (WNP) induces an anticyclonic anomaly, and this anticyclonic anomaly results in more rainfall along the East Asian rain band through more water vapor transport during summer, as well as early and middle summer. However, the present results indicate that during late summer (from mid-August to the beginning of September), the anomalous anticyclone leads to more rainfall over central southern China (CSC), a region quite different from preceding periods. The uniqueness of late summer is found to be related to the dramatic change in climatological monsoon flows: southerlies over southern China during early and middle summer but easterlies during late summer. Therefore, the anomalous anticyclone, which shows a southerly anomaly over southern China, enhances monsoonal southerlies and induces more rainfall along the rain band during early and middle summer. During late summer, however, the anomalous anticyclone reflects a complicated change in monsoon flows: it changes the path, rather than the intensity, of monsoon flows. Specifically, during late summers of suppressed convection in the tropical WNP, southerlies dominate from the South China Sea to southern China, and during late summers of enhanced convection, northeasterlies dominate from the East China Sea to southern China, causing more and less rainfall in CSC, respectively.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8130-6
Issue No: Vol. 36, No. 3 (2019)

• The Relationship between Deterministic and Ensemble Mean Forecast Errors
Revealed by Global and Local Attractor Radii
• Authors: Jie Feng; Jianping Li; Jing Zhang; Deqiang Liu; Ruiqiang Ding
Pages: 271 - 278
Abstract: It has been demonstrated that ensemble mean forecasts, in the context of the sample mean, have higher forecasting skill than deterministic (or single) forecasts. However, few studies have focused on quantifying the relationship between their forecast errors, especially in individual prediction cases. Clarification of the characteristics of deterministic and ensemble mean forecasts from the perspective of attractors of dynamical systems has also rarely been involved. In this paper, two attractor statistics—namely, the global and local attractor radii (GAR and LAR, respectively)—are applied to reveal the relationship between deterministic and ensemble mean forecast errors. The practical forecast experiments are implemented in a perfect model scenario with the Lorenz96 model as the numerical results for verification. The sample mean errors of deterministic and ensemble mean forecasts can be expressed by GAR and LAR, respectively, and their ratio is found to approach $$\sqrt 2$$ with lead time. Meanwhile, the LAR can provide the expected ratio of the ensemble mean and deterministic forecast errors in individual cases.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8123-5
Issue No: Vol. 36, No. 3 (2019)

• Global Monsoon Changes under the Paris Agreement Temperature Goals in
CESM1(CAM5)
• Authors: Xia Qu; Gang Huang
Pages: 279 - 291
Abstract: Based on experiments with the Community Earth System Model, version 1 (Community Atmosphere Model, version 5) [CESM1(CAM5)], and an observational dataset, we found that CESM1-CAM5 is able to reproduce global monsoon (GM) features, including the patterns of monsoon precipitation and monsoon domains, the magnitude of GM precipitation (GMP, the local summer precipitation), GM area (GMA), and GM percentage (the ratio of the local summer precipitation to annual precipitation). Under the Paris Agreement temperature goals, the GM in CESM1-CAM5 displays the following changes: (1) The GMA is ambiguous under the 1.5°C temperature goal and increases under the 2.0°C temperature goal. The increase mainly results from a change in the monsoon percentage. (2) The GM, land monsoon and ocean monsoon precipitation all significantly increase under both the 1.5°C and 2.0°C goals. The increases are mainly due to the enhancement of humidity and evaporation. (3) The percentages of GM, land monsoon and ocean monsoon feature little change under the temperature goals. (4) The lengths of the GM, land monsoon and ocean monsoon are significantly prolonged under the temperature goals. The increase in precipitation during the monsoon withdrawal month mainly accounts for the prolonged monsoons. Regarding the differences between the 1.5°C and 2.0°C temperature goals, it is certain that the GMP displays significant discrepancies. In addition, a large-scale enhancement of ascending motion occurs over the southeastern Tibetan Plateau and South China under a warming climate, whereas other monsoon areas experience an overall decline in ascending motion. This leads to an extraordinary wetting over Asian monsoon areas.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8138-y
Issue No: Vol. 36, No. 3 (2019)

• Verification and Improvement of the Ability of CFSv2 to Predict the
Antarctic Oscillation in Boreal Spring
• Authors: Dapeng Zhang; Yanyan Huang; Bo Sun; Fei Li; Huijun Wang
Pages: 292 - 302
Abstract: The boreal spring Antarctic Oscillation (AAO) has a significant impact on the spring and summer climate in China. This study evaluates the capability of the NCEP’s Climate Forecast System, version 2 (CFSv2), in predicting the boreal spring AAO for the period 1983–2015. The results indicate that CFSv2 has poor skill in predicting the spring AAO, failing to predict the zonally symmetric spatial pattern of the AAO, with an insignificant correlation of 0.02 between the predicted and observed AAO Index (AAOI). Considering the interannual increment approach can amplify the prediction signals, we firstly establish a dynamical–statistical model to improve the interannual increment of the AAOI (DY AAOI), with two predictors of CFSv2-forecasted concurrent spring sea surface temperatures and observed preceding autumn sea ice. This dynamical–statistical model demonstrates good capability in predicting DY AAOI, with a significant correlation coefficient of 0.58 between the observation and prediction during 1983–2015 in the two-year-out cross-validation. Then, we obtain an improved AAOI by adding the improved DY AAOI to the preceding observed AAOI. The improved AAOI shows a significant correlation coefficient of 0.45 with the observed AAOI during 1983–2015. Moreover, the unrealistic atmospheric response to March–April–May sea ice in CFSv2 may be the possible cause for the failure of CFSv2 to predict the AAO. This study gives new clues regarding AAO prediction and short-term climate prediction.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8106-6
Issue No: Vol. 36, No. 3 (2019)

• Determining Atmospheric Boundary Layer Height with the Numerical
Differentiation Method Using Bending Angle Data from COSMIC
• Authors: Shen Yan; Jie Xiang; Huadong Du
Pages: 303 - 312
Abstract: This paper presents a new method to estimate the height of the atmospheric boundary layer (ABL) by using COSMIC radio occultation bending angle (BA) data. Using the numerical differentiation method combined with the regularization technique, the first derivative of BA profiles is retrieved, and the height at which the first derivative of BA has the global minimum is defined to be the ABL height. To reflect the reliability of estimated ABL heights, the sharpness parameter is introduced, according to the relative minimum of the BA derivative. Then, it is applied to four months of COSMIC BA data (January, April, July, and October in 2008), and the ABL heights estimated are compared with two kinds of ABL heights from COSMIC products and with the heights determined by the finite difference method upon the refractivity data. For sharp ABL tops (large sharpness parameters), there is little difference between the ABL heights determined by different methods, i.e., the uncertainties are small; whereas, for non-sharp ABL tops (small sharpness parameters), big differences exist in the ABL heights obtained by different methods, which means large uncertainties for different methods. In addition, the new method can detect thin ABLs and provide a reference ABL height in the cases eliminated by other methods. Thus, the application of the numerical differentiation method combined with the regularization technique to COSMIC BA data is an appropriate choice and has further application value.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-7308-2
Issue No: Vol. 36, No. 3 (2019)

• Tides and Turbulent Mixing in the North of Taiwan Island
• Authors: Xiangzhou Song; Dexing Wu; Xiaohui Xie
Pages: 313 - 325
Abstract: Microstructure and hydrological profiles were collected along two cross-shelf sections from the deep slope to the shallow water in the north of Taiwan Island in the summer of 2006. While the tidal currents on the shelf were dominated by the barotropic tide with the current ellipse stretched across the shelf, significant internal tides were observed on the slope. The depth-mean turbulent kinetic energy (TKE) dissipation rate on the shelf was 10−6 W kg−1, corresponding to a diapycnal diffusivity of 10−2 m2 s−1. The depth-mean TKE dissipation rate on the slope was 1×10−7 Wkg−1, with diapycnal diffusivity of 3.4×10−4 m2 s−1. The shear instability associated with internal tides largely contributed to the TKE dissipation rate on the slope from the surface to 150 m, while the enhanced turbulence on the shelf was dominated by tidal or residual current dissipations caused by friction in the thick bottom boundary layer (BBL). In the BBL, the Ekman currents associated with the northeastward Taiwan Warm Current were identified, showing a near-bottom velocity spiral, which agreed well with the analytical bottom Ekman solution.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-8098-2
Issue No: Vol. 36, No. 3 (2019)

• Evaluation of Summer Monsoon Clouds over the Tibetan Plateau Simulated in
the ACCESS Model Using Satellite Products
• Authors: Liang Hu; Zhian Sun; Difei Deng; Greg Roff
Pages: 326 - 338
Abstract: Cloud distribution characteristics over the Tibetan Plateau in the summer monsoon period simulated by the Australian Community Climate and Earth System Simulator (ACCESS) model are evaluated using COSP [the CFMIP (Cloud Feedback Model Intercomparison Project) Observation Simulator Package]. The results show that the ACCESS model simulates less cumulus cloud at atmospheric middle levels when compared with observations from CALIPSO and CloudSat, but more ice cloud at high levels and drizzle drops at low levels. The model also has seasonal biases after the onset of the summer monsoon in May. While observations show that the prevalent high cloud at 9–10 km in spring shifts downward to 7–9 km, the modeled maximum cloud fractions move upward to 12–15 km. The reason for this model deficiency is investigated by comparing model dynamical and thermodynamical fields with those of ERA-Interim. It is found that the lifting effect of the Tibetan Plateau in the ACCESS model is stronger than in ERA-Interim, which means that the vertical velocity in the ACCESS model is stronger and more water vapor is transported to the upper levels of the atmosphere, resulting in more high-level ice clouds and less middle-level cumulus cloud over the Tibetan Plateau. The modeled radiation fields and precipitation are also evaluated against the relevant satellite observations.
PubDate: 2019-03-01
DOI: 10.1007/s00376-018-7301-9
Issue No: Vol. 36, No. 3 (2019)

• Performance of the Wind Farm Parameterization Scheme Coupled with the
Weather Research and Forecasting Model under Multiple Resolution Regimes
for Simulating an Onshore Wind Farm
• Authors: Rajabu J. Mangara; Zhenhai Guo; Shuanglin Li
Pages: 119 - 132
Abstract: We use theWind Farm Parameterization (WFP) scheme coupled with theWeather Research and Forecasting model under multiple resolution regimes to simulate turbulent wake dynamics generated by a real onshore wind farm and their influence at the local meteorological scale. The model outputs are compared with earlier modeling and observation studies. It is found that higher vertical and horizontal resolutions have great impacts on the simulated wake flow dynamics. The corresponding wind speed deficit and turbulent kinetic energy results match well with previous studies. In addition, the effect of horizontal resolution on near-surface meteorology is significantly higher than that of vertical resolution. The wake flow field extends from the start of the wind farm to downstream within 10 km, where the wind speed deficit may exceed 4%. For a height of 150 m or at a distance of about 25 km downstream, the wind speed deficit is around 2%. This indicates that, at a distance of more than 25 km downstream, the impact of the wind turbines can be ignored. Analysis of near-surface meteorology indicates a night and early morning warming near the surface, and increase in near-surface water vapor mixing ratio with decreasing surface sensible and latent heat fluxes. During daytime, a slight cooling near the surface and decrease in the near-surface water vapor mixing ratio with increasing surface sensible and latent heat fluxes is noticed over the wind farm area.
PubDate: 2019-02-01
DOI: 10.1007/s00376-018-8028-3
Issue No: Vol. 36, No. 2 (2019)

• Impact of the Assimilation Frequency of Radar Data with the ARPS 3DVar and
Cloud Analysis System on Forecasts of a Squall Line in Southern China
• Authors: Yujie Pan; Mingjun Wang
Pages: 160 - 172
Abstract: Assimilation configurations have significant impacts on analysis results and subsequent forecasts. A squall line system that occurred on 23 April 2007 over southern China was used to investigate the impacts of the data assimilation frequency of radar data on analyses and forecasts. A three-dimensional variational system was used to assimilate radial velocity data, and a cloud analysis system was used for reflectivity assimilation with a 2-h assimilation window covering the initial stage of the squall line. Two operators of radar reflectivity for cloud analyses corresponding to single- and double-moment schemes were used. In this study, we examined the sensitivity of assimilation frequency using 10-, 20-, 30-, and 60-min assimilation intervals. The results showed that analysis fields were not consistent with model dynamics and microphysics in general; thus, model states, including dynamic and microphysical variables, required approximately 20 min to reach a new balance after data assimilation in all experiments. Moreover, a 20-min data assimilation interval generally produced better forecasts for both single- and double-moment schemes in terms of equitable threat and bias scores. We conclude that a higher data assimilation frequency can produce a more intense cold pool and rear inflow jets but does not necessarily lead to a better forecast.
PubDate: 2019-02-01
DOI: 10.1007/s00376-018-8087-5
Issue No: Vol. 36, No. 2 (2019)

• Satellite-based Observational Study of the Tibetan Plateau Vortex:
Features of Deep Convective Cloud Tops
• Authors: Yi-Xuan Shou; Feng Lu; Hui Liu; Peng Cui; Shaowen Shou; Jian Liu
Pages: 189 - 205
Abstract: In this study, an east-moving Tibetan Plateau vortex (TPV) is analyzed by using the ERA-5 reanalysis and multi-source satellite data, including FengYun-2E, Aqua/MODIS and CALIPSO. The objective is to demonstrate: (i) the usefulness of multi-spectral satellite observations in understanding the evolution of a TPV and the associated rainfall, and (ii) the potential significance of cloud-top quantitative information in improving Southwest China weather forecasts. Results in this study show that the heavy rainfall is caused by the coupling of an east-moving TPV and some low-level weather systems [a Plateau shear line and a Southwest Vortex (SWV)], wherein the TPV is a key component. During the TPV’s life cycle, the rainfall and vortex intensity maintain a significant positive correlation with the convective cloud-top fraction and height within a 2.5◦ radius away from its center. Moreover, its growth is found to be quite sensitive to the cloud phases and particle sizes. In the mature stage when the TPV is coupled with an SWV, an increase of small ice crystal particles and appearance of ring- and U/V-shaped cold cloud-top structures can be seen as the signature of a stronger convection and rainfall enhancement within the TPV. A tropopause folding caused by ageostrophic flows at the upper level may be a key factor in the formation of ring-shaped and U/V-shaped cloud-top structures. Based on these results, we believe that the supplementary quantitative information of an east-moving TPV cloud top collected by multi-spectral satellite observations could help to improve Southwest China short-range/nowcasting weather forecasts.
PubDate: 2019-02-01
DOI: 10.1007/s00376-018-8049-y
Issue No: Vol. 36, No. 2 (2019)

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