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Fengjiao Chen
,
Xiaoyi Zheng
,
Huayang Wen
, and
Ye Yuan

Abstract

Precipitation microphysics are critical for precipitation estimation and forecasting in numerical models. Using six years of observations from the Global Precipitation Measurement satellite, the spatial characteristics of precipitation microphysics are examined during the summer monsoon season over the Yangtze–Huaihe River valley. The results indicate that the heaviest convective rainfall is located mainly between the Huaihe and Yangtze Rivers, associated with a smaller mass-weighted mean diameter (Dm = ∼1.65 mm) and a larger mean generalized intercept parameter (Nw ) (∼41 dBNw ) at 2 km in altitude than those over the surrounding regions. Further, the convection in this region also has the lowest polarization-corrected temperature at 89 GHz (PCT89 < 254 K), indicating high concentrations of ice hydrometeors. For a given rainfall intensity, stratiform precipitation is characterized by a smaller mean Dm than convective precipitation. Below 4.5 km in altitude, the vertical slope of medium reflectivity factor varies with the rainfall intensity, which decreases slightly downward for light rain (<2.5 mm h−1), increases slightly for moderate rain (2.5–7.9 mm h−1), and increases more sharply for heavy rain (≥8 mm h−1) for both convective and stratiform precipitation. The increase in the amplitude of heavy rain for stratiform precipitation is much higher than that for convective precipitation, probably due to more efficient growth by warm rain processes. The PCT89 values have a greater potential to inform the near-surface microphysical parameters in convective precipitation compared with stratiform precipitation.

Open access
Jiaxin Ye
,
Chaoxia Yuan
,
Mengzhou Yang
,
Xinyu Lu
,
Jing-Jia Luo
, and
Toshio Yamagata

Abstract

Significant anomalies in frequency of summer extreme hot days (SEHDs) are broadly observed in the Asian monsoon region (AMR) in the post-ENSO summers. The delayed ENSO impacts are mainly conveyed by provoking the Indo-western Pacific Ocean capacitor (IPOC) effect that maintains the anomalous anticyclone in the western North Pacific. The related diabatic heating anomaly can trigger the westward-propagating Rossby wave to the Indian subcontinent, which increases the geopotential heights, reduces the cloud cover, and thus increases the seasonal surface temperature and SEHD frequency in the southern AMR. Besides, the reduced atmospheric moisture in the western North Pacific hinders the northward propagation of intraseasonal oscillation (ISO) and modulates the occurrence frequency of individual ISO phases, contributing to the significantly increased/decreased SEHDs in eastern China/Hokkaido, Japan, in the post–El Niño summers. The 25-model-ensemble mean of CMIP6 historical runs can reproduce well the observed SEHD anomalies in the southern AMR in the post-ENSO summers mainly due to the realistic simulation of ENSO impacts on the seasonal surface temperature, although a large intermodel spread exists due to different strengths of IPOC effect in each model owing to model biases in the mean state of the eastern tropical Pacific, the ENSO variance, and teleconnection to the Indian Ocean. Furthermore, future projections under the SSP5-8.5 scenario show that the delayed ENSO impacts on the southern AMR remain stable under global warming via a similar mechanism as in the observations and historical runs.

Restricted access
Yi Liu
,
Ye Zhu
,
Liliang Ren
,
Jason Otkin
,
Eric D. Hunt
,
Xiaoli Yang
,
Fei Yuan
, and
Shanhu Jiang

Abstract

Flash droughts are extreme phenomena that have been identified using two different approaches. The first approach identifies these events based on unusually rapid intensification rates, whereas the second approach implicitly identifies short-term features. This latter approach classifies flash droughts into two types, namely, precipitation deficit and heat wave flash droughts (denoted as PDFD and HWFD). In this study, we evaluate these two approaches over the Yellow River basin (YRB) to determine which approach provides more accurate information about flash droughts and why. Based on the concept of intensification rate, a new quantitative flash drought identification method focused on soil moisture depletion during the onset–development phase is proposed. Its performance was evaluated by comparing the onset time and spatial dynamics of the identified flash droughts with PDFD and HWFD events identified using the second approach. The results show that the rapid-intensification approach is better able to capture the continuous evolution of a flash drought. Since the approach for identifying PDFD and HWFD events does not consider changes in soil moisture with time, it cannot ensure that the events exhibit rapid intensification, nor can it effectively capture flash droughts’ onset. Evaluation of the results showed that the chosen hydrometeorological variables and corresponding thresholds, particularly that of temperature, are the main reasons for the poor performance of the PDFD and HWFD identification approach. This study promotes a deeper understanding of flash droughts that is beneficial for drought monitoring, early warning, and mitigation.

Free access
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.

Free access
Robert J. H. Dunn
,
Freya Aldred
,
Nadine Gobron
,
John B. Miller
,
Kate M. Willett
,
Melanie Ades
,
Robert Adler
,
R. P. Allan
,
John Anderson
,
Orlane Anneville
,
Yasuyuki Aono
,
Anthony Argüez
,
Carlo Arosio
,
John A. Augustine
,
Cesar Azorin-Molina
,
Jonathan Barichivich
,
Aman Basu
,
Hylke E. Beck
,
Nicolas Bellouin
,
Angela Benedetti
,
Kevin Blagrave
,
Stephen Blenkinsop
,
Olivier Bock
,
Xavier Bodin
,
Michael G. Bosilovich
,
Olivier Boucher
,
Gerald Bove
,
Dennis Buechler
,
Stefan A. Buehler
,
Laura Carrea
,
Kai-Lan Chang
,
Hanne H. Christiansen
,
John R. Christy
,
Eui-Seok Chung
,
Laura M. Ciasto
,
Melanie Coldewey-Egbers
,
Owen R. Cooper
,
Richard C. Cornes
,
Curt Covey
,
Thomas Cropper
,
Molly Crotwell
,
Diego Cusicanqui
,
Sean M. Davis
,
Richard A. M. de Jeu
,
Doug Degenstein
,
Reynald Delaloye
,
Markus G. Donat
,
Wouter A. Dorigo
,
Imke Durre
,
Geoff S. Dutton
,
Gregory Duveiller
,
James W. Elkins
,
Thomas W. Estilow
,
Nava Fedaeff
,
David Fereday
,
Vitali E. Fioletov
,
Johannes Flemming
,
Michael J. Foster
,
Stacey M. Frith
,
Lucien Froidevaux
,
Martin Füllekrug
,
Judith Garforth
,
Jay Garg
,
Matthew Gentry
,
Steven Goodman
,
Qiqi Gou
,
Nikolay Granin
,
Mauro Guglielmin
,
Sebastian Hahn
,
Leopold Haimberger
,
Brad D. Hall
,
Ian Harris
,
Debbie L. Hemming
,
Martin Hirschi
,
Shu-pen (Ben) Ho
,
Robert Holzworth
,
Filip Hrbáček
,
Daan Hubert
,
Petra Hulsman
,
Dale F. Hurst
,
Antje Inness
,
Ketil Isaksen
,
Viju O. John
,
Philip D. Jones
,
Robert Junod
,
Andreas Kääb
,
Johannes W. Kaiser
,
Viktor Kaufmann
,
Andreas Kellerer-Pirklbauer
,
Elizabeth C. Kent
,
Richard Kidd
,
Hyungiun Kim
,
Zak Kipling
,
Akash Koppa
,
Jan Henning L’Abée-Lund
,
Xin Lan
,
Kathleen O. Lantz
,
David Lavers
,
Norman G. Loeb
,
Diego Loyola
,
Remi Madelon
,
Hilmar J. Malmquist
,
Wlodzimierz Marszelewski
,
Michael Mayer
,
Matthew F. McCabe
,
Tim R. McVicar
,
Carl A. Mears
,
Annette Menzel
,
Christopher J. Merchant
,
Diego G. Miralles
,
Stephen A. Montzka
,
Colin Morice
,
Leander Mösinger
,
Jens Mühle
,
Julien P. Nicolas
,
Jeannette Noetzli
,
Tiina Nõges
,
Ben Noll
,
John O’Keefe
,
Tim J. Osborn
,
Taejin Park
,
Cecile Pellet
,
Maury S. Pelto
,
Sarah E. Perkins-Kirkpatrick
,
Coda Phillips
,
Stephen Po-Chedley
,
Lorenzo Polvani
,
Wolfgang Preimesberger
,
Colin Price
,
Merja Pulkkanen
,
Dominik G. Rains
,
William J. Randel
,
Samuel Rémy
,
Lucrezia Ricciardulli
,
Andrew D. Richardson
,
David A. Robinson
,
Matthew Rodell
,
Nemesio J. Rodríguez-Fernández
,
Karen H. Rosenlof
,
Chris Roth
,
Alexei Rozanov
,
This Rutishäuser
,
Ahira Sánchez-Lugo
,
Parnchai Sawaengphokhai
,
Verena Schenzinger
,
Robert W. Schlegel
,
Udo Schneider
,
Sapna Sharma
,
Lei Shi
,
Adrian J. Simmons
,
Carolina Siso
,
Sharon L. Smith
,
Brian J. Soden
,
Viktoria Sofieva
,
Tim H. Sparks
,
Paul W. Stackhouse Jr.
,
Ryan Stauffer
,
Wolfgang Steinbrecht
,
Andrea K. Steiner
,
Kenton Stewart
,
Pietro Stradiotti
,
Dimitri A. Streletskiy
,
Hagen Telg
,
Stephen J. Thackeray
,
Emmanuel Thibert
,
Michael Todt
,
Daisuke Tokuda
,
Kleareti Tourpali
,
Mari R. Tye
,
Ronald van der A
,
Robin van der Schalie
,
Gerard van der Schrier
,
Mendy van der Vliet
,
Guido R. van der Werf
,
Arnold. van Vliet
,
Jean-Paul Vernier
,
Isaac J. Vimont
,
Katrina Virts
,
Sebastiàn Vivero
,
Holger Vömel
,
Russell S. Vose
,
Ray H. J. Wang
,
Markus Weber
,
David Wiese
,
Jeanette D. Wild
,
Earle Williams
,
Takmeng Wong
,
R. I. Woolway
,
Xungang Yin
,
Ye Yuan
,
Lin Zhao
,
Xinjia Zhou
,
Jerry R. Ziemke
,
Markus Ziese
, and
Ruxandra M. Zotta
Free access