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Yihong Duan
,
Qilin Wan
,
Jian Huang
,
Kun Zhao
,
Hui Yu
,
Yuqing Wang
,
Dajun Zhao
,
Jianing Feng
,
Jie Tang
,
Peiyan Chen
,
Xiaoqin Lu
,
Yuan Wang
,
Jianyin Liang
,
Liguang Wu
,
Xiaopeng Cui
,
Jing Xu
, and
Pak-Wai Chan

Abstract

Landfalling tropical cyclones (TCs) often experience drastic changes in their motion, intensity, and structure due to complex multiscale interactions among atmospheric processes and among the coastal ocean, land, and atmosphere. Because of the lack of comprehensive data and low capability of numerical models, understanding of and ability to predict landfalling TCs are still limited. A 10-yr key research project on landfalling TCs was initiated and launched in 2009 in China. The project has been jointly supported by the China Ministry of Science and Technology, China Meteorological Administration (CMA), Ministry of Education, and Chinese Academy of Sciences. Its mission is to enhance understanding of landfalling TC processes and improve forecasting skills on track, intensity, and distributions of strong winds and precipitation in landfalling TCs. This article provides an overview of the project, together with highlights of some new findings and new technical developments, as well as planned future efforts.

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Tandong Yao
,
Yongkang Xue
,
Deliang Chen
,
Fahu Chen
,
Lonnie Thompson
,
Peng Cui
,
Toshio Koike
,
William K.-M. Lau
,
Dennis Lettenmaier
,
Volker Mosbrugger
,
Renhe Zhang
,
Baiqing Xu
,
Jeff Dozier
,
Thomas Gillespie
,
Yu Gu
,
Shichang Kang
,
Shilong Piao
,
Shiori Sugimoto
,
Kenichi Ueno
,
Lei Wang
,
Weicai Wang
,
Fan Zhang
,
Yongwei Sheng
,
Weidong Guo
,
Ailikun
,
Xiaoxin Yang
,
Yaoming Ma
,
Samuel S. P. Shen
,
Zhongbo Su
,
Fei Chen
,
Shunlin Liang
,
Yimin Liu
,
Vijay P. Singh
,
Kun Yang
,
Daqing Yang
,
Xinquan Zhao
,
Yun Qian
,
Yu Zhang
, and
Qian Li

Abstract

The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2,000 years. This paper reviews the latest development in multidisciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of the TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends, although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that mesoscale convective systems play in the TP’s precipitation as well as an association between soil moisture anomalies in the TP and the Indian monsoon. Moreover, an increase in geohazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.

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Weiqing Qu
,
A. Henderson-Sellers
,
A. J. Pitman
,
T. H. Chen
,
F. Abramopoulos
,
A. Boone
,
S. Chang
,
F. Chen
,
Y. Dai
,
R. E. Dickinson
,
L. Dümenil
,
M. Ek
,
N. Gedney
,
Y. M. Gusev
,
J. Kim
,
R. Koster
,
E. A. Kowalczyk
,
J. Lean
,
D. Lettenmaier
,
X. Liang
,
J.-F. Mahfouf
,
H.-T. Mengelkamp
,
K. Mitchell
,
O. N. Nasonova
,
J. Noilhan
,
A. Robock
,
C. Rosenzweig
,
J. Schaake
,
C. A. Schlosser
,
J.-P. Schulz
,
A. B. Shmakin
,
D. L. Verseghy
,
P. Wetzel
,
E. F. Wood
,
Z.-L. Yang
, and
Q. Zeng

Abstract

In the PILPS Phase 2a experiment, 23 land-surface schemes were compared in an off-line control experiment using observed meteorological data from Cabauw, the Netherlands. Two simple sensitivity experiments were also undertaken in which the observed surface air temperature was artificially increased or decreased by 2 K while all other factors remained as observed. On the annual timescale, all schemes show similar responses to these perturbations in latent, sensible heat flux, and other key variables. For the 2-K increase in temperature, surface temperatures and latent heat fluxes all increase while net radiation, sensible heat fluxes, and soil moistures all decrease. The results are reversed for a 2-K temperature decrease. The changes in sensible heat fluxes and, especially, the changes in the latent heat fluxes are not linearly related to the change of temperature. Theoretically, the nonlinear relationship between air temperature and the latent heat flux is evident and due to the convex relationship between air temperature and saturation vapor pressure. A simple test shows that, the effect of the change of air temperature on the atmospheric stratification aside, this nonlinear relationship is shown in the form that the increase of the latent heat flux for a 2-K temperature increase is larger than its decrease for a 2-K temperature decrease. However, the results from the Cabauw sensitivity experiments show that the increase of the latent heat flux in the +2-K experiment is smaller than the decrease of the latent heat flux in the −2-K experiment (we refer to this as the asymmetry). The analysis in this paper shows that this inconsistency between the theoretical relationship and the Cabauw sensitivity experiments results (or the asymmetry) is due to (i) the involvement of the β g formulation, which is a function of a series stress factors that limited the evaporation and whose values change in the ±2-K experiments, leading to strong modifications of the latent heat flux; (ii) the change of the drag coefficient induced by the changes in stratification due to the imposed air temperature changes (±2 K) in parameterizations of latent heat flux common in current land-surface schemes. Among all stress factors involved in the β g formulation, the soil moisture stress in the +2-K experiment induced by the increased evaporation is the main factor that contributes to the asymmetry.

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T. H. Chen
,
A. Henderson-Sellers
,
P. C. D. Milly
,
A. J. Pitman
,
A. C. M. Beljaars
,
J. Polcher
,
F. Abramopoulos
,
A. Boone
,
S. Chang
,
F. Chen
,
Y. Dai
,
C. E. Desborough
,
R. E. Dickinson
,
L. Dümenil
,
M. Ek
,
J. R. Garratt
,
N. Gedney
,
Y. M. Gusev
,
J. Kim
,
R. Koster
,
E. A. Kowalczyk
,
K. Laval
,
J. Lean
,
D. Lettenmaier
,
X. Liang
,
J.-F. Mahfouf
,
H.-T. Mengelkamp
,
K. Mitchell
,
O. N. Nasonova
,
J. Noilhan
,
A. Robock
,
C. Rosenzweig
,
J. Schaake
,
C. A. Schlosser
,
J.-P. Schulz
,
Y. Shao
,
A. B. Shmakin
,
D. L. Verseghy
,
P. Wetzel
,
E. F. Wood
,
Y. Xue
,
Z.-L. Yang
, and
Q. Zeng

Abstract

In the Project for Intercomparison of Land-Surface Parameterization Schemes phase 2a experiment, meteorological data for the year 1987 from Cabauw, the Netherlands, were used as inputs to 23 land-surface flux schemes designed for use in climate and weather models. Schemes were evaluated by comparing their outputs with long-term measurements of surface sensible heat fluxes into the atmosphere and the ground, and of upward longwave radiation and total net radiative fluxes, and also comparing them with latent heat fluxes derived from a surface energy balance. Tuning of schemes by use of the observed flux data was not permitted. On an annual basis, the predicted surface radiative temperature exhibits a range of 2 K across schemes, consistent with the range of about 10 W m−2 in predicted surface net radiation. Most modeled values of monthly net radiation differ from the observations by less than the estimated maximum monthly observational error (±10 W m−2). However, modeled radiative surface temperature appears to have a systematic positive bias in most schemes; this might be explained by an error in assumed emissivity and by models’ neglect of canopy thermal heterogeneity. Annual means of sensible and latent heat fluxes, into which net radiation is partitioned, have ranges across schemes of30 W m−2 and 25 W m−2, respectively. Annual totals of evapotranspiration and runoff, into which the precipitation is partitioned, both have ranges of 315 mm. These ranges in annual heat and water fluxes were approximately halved upon exclusion of the three schemes that have no stomatal resistance under non-water-stressed conditions. Many schemes tend to underestimate latent heat flux and overestimate sensible heat flux in summer, with a reverse tendency in winter. For six schemes, root-mean-square deviations of predictions from monthly observations are less than the estimated upper bounds on observation errors (5 W m−2 for sensible heat flux and 10 W m−2 for latent heat flux). Actual runoff at the site is believed to be dominated by vertical drainage to groundwater, but several schemes produced significant amounts of runoff as overland flow or interflow. There is a range across schemes of 184 mm (40% of total pore volume) in the simulated annual mean root-zone soil moisture. Unfortunately, no measurements of soil moisture were available for model evaluation. A theoretical analysis suggested that differences in boundary conditions used in various schemes are not sufficient to explain the large variance in soil moisture. However, many of the extreme values of soil moisture could be explained in terms of the particulars of experimental setup or excessive evapotranspiration.

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X. Liang
,
S. Miao
,
J. Li
,
R. Bornstein
,
X. Zhang
,
Y. Gao
,
F. Chen
,
X. Cao
,
Z. Cheng
,
C. Clements
,
W. Dabberdt
,
A. Ding
,
D. Ding
,
J. J. Dou
,
J. X. Dou
,
Y. Dou
,
C. S. B. Grimmond
,
J. E. González-Cruz
,
J. He
,
M. Huang
,
X. Huang
,
S. Ju
,
Q. Li
,
D. Niyogi
,
J. Quan
,
J. Sun
,
J. Z. Sun
,
M. Yu
,
J. Zhang
,
Y. Zhang
,
X. Zhao
,
Z. Zheng
, and
M. Zhou

Abstract

Urbanization modifies atmospheric energy and moisture balances, forming distinct features [e.g., urban heat islands (UHIs) and enhanced or decreased precipitation]. These produce significant challenges to science and society, including rapid and intense flooding, heat waves strengthened by UHIs, and air pollutant haze. The Study of Urban Impacts on Rainfall and Fog/Haze (SURF) has brought together international expertise on observations and modeling, meteorology and atmospheric chemistry, and research and operational forecasting. The SURF overall science objective is a better understanding of urban, terrain, convection, and aerosol interactions for improved forecast accuracy. Specific objectives include a) promoting cooperative international research to improve understanding of urban summer convective precipitation and winter particulate episodes via extensive field studies, b) improving high-resolution urban weather and air quality forecast models, and c) enhancing urban weather forecasts for societal applications (e.g., health, energy, hydrologic, climate change, air quality, planning, and emergency response management). Preliminary SURF observational and modeling results are shown (i.e., turbulent PBL structure, bifurcating thunderstorms, haze events, urban canopy model development, and model forecast evaluation).

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Yongkang Xue
,
Ismaila Diallo
,
Aaron A. Boone
,
Tandong Yao
,
Yang Zhang
,
Xubin Zeng
,
J. David Neelin
,
William K. M. Lau
,
Yan Pan
,
Ye Liu
,
Xiaoduo Pan
,
Qi Tang
,
Peter J. van Oevelen
,
Tomonori Sato
,
Myung-Seo Koo
,
Stefano Materia
,
Chunxiang Shi
,
Jing Yang
,
Constantin Ardilouze
,
Zhaohui Lin
,
Xin Qi
,
Tetsu Nakamura
,
Subodh K. Saha
,
Retish Senan
,
Yuhei Takaya
,
Hailan Wang
,
Hongliang Zhang
,
Mei Zhao
,
Hara Prasad Nayak
,
Qiuyu Chen
,
Jinming Feng
,
Michael A. Brunke
,
Tianyi Fan
,
Songyou Hong
,
Paulo Nobre
,
Daniele Peano
,
Yi Qin
,
Frederic Vitart
,
Shaocheng Xie
,
Yanling Zhan
,
Daniel Klocke
,
Ruby Leung
,
Xin Li
,
Michael Ek
,
Weidong Guo
,
Gianpaolo Balsamo
,
Qing Bao
,
Sin Chan Chou
,
Patricia de Rosnay
,
Yanluan Lin
,
Yuejian Zhu
,
Yun Qian
,
Ping Zhao
,
Jianping Tang
,
Xin-Zhong Liang
,
Jinkyu Hong
,
Duoying Ji
,
Zhenming Ji
,
Yuan Qiu
,
Shiori Sugimoto
,
Weicai Wang
,
Kun Yang
, and
Miao Yu

Abstract

Subseasonal-to-seasonal (S2S) precipitation prediction in boreal spring and summer months, which contains a significant number of high-signal events, is scientifically challenging and prediction skill has remained poor for years. Tibetan Plateau (TP) spring observed surface ­temperatures show a lag correlation with summer precipitation in several remote regions, but current global land–atmosphere coupled models are unable to represent this behavior due to significant errors in producing observed TP surface temperatures. To address these issues, the Global Energy and Water Exchanges (GEWEX) program launched the “Impact of Initialized Land Temperature and Snowpack on Subseasonal-to-Seasonal Prediction” (LS4P) initiative as a community effort to test the impact of land temperature in high-mountain regions on S2S prediction by climate models: more than 40 institutions worldwide are participating in this project. After using an innovative new land state initialization approach based on observed surface 2-m temperature over the TP in the LS4P experiment, results from a multimodel ensemble provide evidence for a causal relationship in the observed association between the Plateau spring land temperature and summer precipitation over several regions across the world through teleconnections. The influence is underscored by an out-of-phase oscillation between the TP and Rocky Mountain surface temperatures. This study reveals for the first time that high-mountain land temperature could be a substantial source of S2S precipitation predictability, and its effect is probably as large as ocean surface temperature over global “hotspot” regions identified here; the ensemble means in some “hotspots” produce more than 40% of the observed anomalies. This LS4P approach should stimulate more follow-on explorations.

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C. P. Weaver
,
X.-Z. Liang
,
J. Zhu
,
P. J. Adams
,
P. Amar
,
J. Avise
,
M. Caughey
,
J. Chen
,
R. C. Cohen
,
E. Cooter
,
J. P. Dawson
,
R. Gilliam
,
A. Gilliland
,
A. H. Goldstein
,
A. Grambsch
,
D. Grano
,
A. Guenther
,
W. I. Gustafson
,
R. A. Harley
,
S. He
,
B. Hemming
,
C. Hogrefe
,
H.-C. Huang
,
S. W. Hunt
,
D.J. Jacob
,
P. L. Kinney
,
K. Kunkel
,
J.-F. Lamarque
,
B. Lamb
,
N. K. Larkin
,
L. R. Leung
,
K.-J. Liao
,
J.-T. Lin
,
B. H. Lynn
,
K. Manomaiphiboon
,
C. Mass
,
D. McKenzie
,
L. J. Mickley
,
S. M. O'neill
,
C. Nolte
,
S. N. Pandis
,
P. N. Racherla
,
C. Rosenzweig
,
A. G. Russell
,
E. Salathé
,
A. L. Steiner
,
E. Tagaris
,
Z. Tao
,
S. Tonse
,
C. Wiedinmyer
,
A. Williams
,
D. A. Winner
,
J.-H. Woo
,
S. WU
, and
D. J. Wuebbles

This paper provides a synthesis of results that have emerged from recent modeling studies of the potential sensitivity of U.S. regional ozone (O3) concentrations to global climate change (ca. 2050). This research has been carried out under the auspices of an ongoing U.S. Environmental Protection Agency (EPA) assessment effort to increase scientific understanding of the multiple complex interactions among climate, emissions, atmospheric chemistry, and air quality. The ultimate goal is to enhance the ability of air quality managers to consider global change in their decisions through improved characterization of the potential effects of global change on air quality, including O3 The results discussed here are interim, representing the first phase of the EPA assessment. The aim in this first phase was to consider the effects of climate change alone on air quality, without accompanying changes in anthropogenic emissions of precursor pollutants. Across all of the modeling experiments carried out by the different groups, simulated global climate change causes increases of a few to several parts per billion (ppb) in summertime mean maximum daily 8-h average O3 concentrations over substantial regions of the country. The different modeling experiments in general do not, however, simulate the same regional patterns of change. These differences seem to result largely from variations in the simulated patterns of changes in key meteorological drivers, such as temperature and surface insolation. How isoprene nitrate chemistry is represented in the different modeling systems is an additional critical factor in the simulated O3 response to climate change.

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