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Linda Bogerd
,
Chris Kidd
,
Christian Kummerow
,
Hidde Leijnse
,
Aart Overeem
,
Veljko Petkovic
,
Kirien Whan
, and
Remko Uijlenhoet

Abstract

Spaceborne microwave radiometers represent an important component of the Global Precipitation Measurement (GPM) mission due to their frequent sampling of rain systems. Microwave radiometers measure microwave radiation (brightness temperatures Tb), which can be converted into precipitation estimates with appropriate assumptions. However, detecting shallow precipitation systems using spaceborne radiometers is challenging, especially over land, as their weak signals are hard to differentiate from those associated with dry conditions. This study uses a random forest (RF) model to classify microwave radiometer observations as dry, shallow, or nonshallow over the Netherlands—a region with varying surface conditions and frequent occurrence of shallow precipitation. The RF model is trained on five years of data (2016–20) and tested with two independent years (2015 and 2021). The observations are classified using ground-based weather radar echo top heights. Various RF models are assessed, such as using only GPM Microwave Imager (GMI) Tb values as input features or including spatially aligned ERA5 2-m temperature and freezing level reanalysis and/or Dual-Frequency Precipitation Radar (DPR) observations. Independent of the input features, the model performs best in summer and worst in winter. The model classifies observations from high-frequency channels (≥85 GHz) with lower Tb values as nonshallow, higher values as dry, and those in between as shallow. Misclassified footprints exhibit radiometric characteristics corresponding to their assigned class. Case studies reveal dry observations misclassified as shallow are associated with lower Tb values, likely resulting from the presence of ice particles in nonprecipitating clouds. Shallow footprints misclassified as dry are likely related to the absence of ice particles.

Significance Statement

Published research concerning rainfall retrieval algorithms from microwave radiometers is often focused on the accuracy of these algorithms. While shallow precipitation over land is often characterized as problematic in these studies, little progress has been made with these systems. In particular, precipitation formed by shallow clouds, where shallow refers to the clouds being close to Earth’s surface, is often missed. This study is focused on detecting shallow precipitation and its physical characteristics to further improve its detection from spaceborne sensors. As such, it contributes to understanding which shallow precipitation scenes are challenging to detect from microwave radiometers, suggesting possible ways for algorithm improvement.

Open access
Alberto Troccoli
,
Tobias Fuchs
,
Roberta Boscolo
,
Elah Matt
, and
Hamid Bastani

Abstract

Weather and Climate Services (W&CS) are key to supporting the transition to net-zero emissions in the energy sector. These services are utilised to increase energy system resilience, enhance renewable energy deployment, and enable uptake of energy-efficiency measures and innovations. As energy systems become increasingly dependent on and affected by weather and climatic conditions, integrating weather and climate data into energy management systems is essential.

This paper addresses the gap in comprehensive guidance for developing integrated W&CS to support net-zero energy transitions, drawing upon a report by the World Meteorological Organization’s Services Commission Study Group on Integrated Energy Services (WMO 2023). We present a framework for co-production of W&CS, exploring how the uptake of W&CS for energy transitions can be enabled through evaluation of socio-economic benefits, harnessing business models, identification of key policies, and capacity development measures.

To support the uptake of W&CS for net-zero energy transitions we recommend: a deeper understanding of user needs and requirements; continuous advancements in the science and technology of W&CS; effective integration of weather and climate data within energy conversion models; improved accessibility and sharing of meteorological and, especially, energy data; promotion of co-production approaches; exploration of novel applications of W&CS in the energy sector; refinement of business models for sustainable W&CS delivery; execution of capacity-building activities; enhanced communication among stakeholders and strengthened collaborative efforts. These steps are crucial for realizing the full potential of W&CS in driving the energy sector towards a sustainable, net-zero future.

Open access
E. Katragkou
,
S. P. Sobolowski
,
C. Teichmann
,
F. Solmon
,
V. Pavlidis
,
D. Rechid
,
P. Hoffmann
,
J. Fernandez
,
G. Nikulin
, and
D. Jacob

Abstract

The Coordinated Regional Downscaling Experiment (CORDEX) is a coordinated international activity that has produced ensembles of regional climate simulations with domains that cover all land areas of the world. These ensembles are used by a wide range of practitioners that include the scientific community, policymakers, and stakeholders from the public and private sectors. They also provide the scientific basis for the Intergovernmental Panel on Climate Change-Assessment Reports. As its next phase now launches, the CMIP6-CORDEX datasets are expected to populate community repositories over the next couple of years, with updated state-of-the-art regional climate data that will further support national and regional communities and inform their climate adaptation and mitigation strategies. The protocol presented here focuses on the European domain (EURO-CORDEX). It takes the international CORDEX protocol covering all 14 global domains as its template. However, it expands on the international protocol in specific areas; incorporates historical and projected aerosol trends into the regional models in a consistent way with CMIP6 global climate models, to allow for a better comparison of global versus regional trends; produces more climate variables to better support sectorial climate impact assessments; and takes into account the recent scientific developments addressed in the CORDEX Flagship Pilot Studies, enabling a better assessment of processes and phenomena relevant to regional climate (e.g., land-use change, aerosol, convection, and urban environment). Here, we summarize the scientific analysis which led to the new simulation protocol and highlight the improvements we expect in the new generation regional climate ensemble.

Open access
Detlef Stammer
,
Daniel E. Amrhein
,
Magdalena Alonso Balmaseda
,
Laurent Bertino
,
Massimo Bonavita
,
Carlo Buontempo
,
Nico Caltabiano
,
Francois Counillon
,
Ian Fenty
,
Raffaele Ferrari
,
Yosuke Fujii
,
Shreyas Sunil Gaikwad
,
Pierre Gentine
,
Andrew Gettelman
,
Ganesh Gopalakrishnan
,
Patrick Heimbach
,
Hans Hersbach
,
Chris Hill
,
Shinya Kobayashi
,
Armin Köhl
,
Paul J. Kushner
,
Matthew Mazloff
,
Hisashi Nakamura
,
Stephen G. Penny
,
Laura Slivinski
,
Susann Tegtmeier
, and
Laure Zanna
Open access
Emiel van der Plas
,
Aart Overeem
,
Jan Fokke Meirink
,
Hidde Leijnse
, and
Linda Bogerd

Abstract

A new pan-European climatological dataset was recently released that has a much higher spatiotemporal resolution than existing pan-European interpolated rain gauge datasets. This radar dataset of hourly precipitation accumulations, EURADCLIM (Overeem et al. 2023), covers most of continental Europe with a resolution of 2 km × 2 km, and is adjusted employing data from potentially thousands of government rain gauges. This study aims to use this dataset to evaluate two important satellite-derived precipitation products over the period 2013 to 2019 at a much higher spatiotemporal resolution than was previously possible at the European scale: the IMERG late run and the Meteosat Second Generation (MSG) Cloud Physical Properties product from the SEVIRI instrument. The latter is only available during daytime, so the analyses are restricted to daytime conditions. A direct grid cell comparison of hourly precipitation reveals an apparently low coefficient of correlation. However, looking into slightly more detail at statistics pertaining to longer time scales or specific areas, the datasets show good correspondence. All datasets are shown to have their specific biases, that can be transient or more systematic, depending on the timing or location. The MSG precipitation seems to have an overall positive bias and the IMERG dataset suffers from some transient overestimation of certain events.

Restricted access
Emily J. Becker
and
Michael K. Tippett

Abstract

The effect of the El Niño–Southern Oscillation (ENSO) teleconnection and climate change trends on observed North American wintertime daily 2-m temperature is investigated for 1960–2022 with a quantile regression model, which represents the variability of the full distribution of daily temperature, including extremes and changes in spread. Climate change trends are included as a predictor in the regression model to avoid the potentially confounding effect on ENSO teleconnections. Based on prior evidence of asymmetric impacts from El Niño and La Niña, the ENSO response is taken to be piecewise linear, and the regression model contains separate predictors for warm and cool ENSO. The relationship between these predictors and shifts in median, interquartile range, skewness, and kurtosis of daily 2-m temperature are summarized through Legendre polynomials. Warm ENSO conditions result in significant warming shifts in the median and contraction of the interquartile range in central-northern North America, while no opposite effect is found for cool ENSO conditions in this region. In the southern United States, cool ENSO conditions produce a warming shift in the median, while warm ENSO conditions have little impact on the median, but contracts the interquartile range. Climate change trends are present as a near-uniform warming in the median and across quantiles and have no discernable impact on interquartile range or higher-order moments. Trends and ENSO together explain a substantial fraction of the interannual variability of daily temperature distribution shifts across much of North America and, to a lesser extent, changes of the interquartile range.

Restricted access
Ruping Huang
,
Shangfeng Chen
,
Wen Chen
,
Renguang Wu
,
Zhibiao Wang
,
Peng Hu
,
Liang Wu
,
Lei Wang
, and
Jingliang Huangfu

Abstract

The poleward migration of tropical cyclone (TC) activity in recent years has been linked to the expansion of the Hadley circulation (HC). Here, we investigate the impact of the winter regional HC over the western Pacific (WPHC) on the frequency of following summer landfalling TC (LTC) in China. Results show that interannual variation of the LTC frequency has a very close connection with the northern WPHC edge (WPHCE). After removing the El Niño–Southern Oscillation signal, there still exists a significant correlation between them. When the winter WPHCE shifts poleward, the associated lower-level southwesterly (easterly) wind anomalies over the subtropical western Pacific (tropical central-eastern Pacific) induce sea surface temperature (SST) warming (cooling) anomalies therein via suppressing (enhancing) upward surface heat flux. In turn, the SST warming (cooling) excites an anomalous cyclonic (anticyclonic) circulation to its west via a Rossby wave response, thus maintaining the southwesterly (easterly) wind anomalies. In addition, the negative rainfall anomalies over the tropical central-eastern Pacific induced by negative SST anomalies can stimulate an anomalous intensive Walker circulation with anomalous upward motion around the tropical western Pacific. Through this positive air–sea interaction, the winter WPHCE signal would be preserved in the ocean and maintained to the succeeding summer, then favoring LTC genesis landward by decreasing the vertical wind shear and increasing the low-level vorticity and midlevel humidity. Meanwhile, anomalous midtropospheric easterly winds over the subtropics are favorable for steering more LTCs toward China’s coast. This study suggests that the winter WPHCE variation is a potential predictor for the prediction of the following summer LTC activity over China.

Significance Statement

Tropical cyclone (TC) is one of the most catastrophic high-impact weather events, which may cause great casualties and severe property losses over the coastal areas, particularly when it makes landfall. Previous research studies have related the poleward migration trend of TC locations to the Hadley circulation (HC) expansion. Compared to the long-term trend, the magnitude of the year-to-year change of the HC edge (HCE) is even larger, leading to a stronger impact on the TC activity. A recent study has suggested that the northern HCE over the western Pacific (WPHCE) in boreal winter exhibits a notable interannual variability. In this study, we reveal that the wintertime WPHCE has a very close connection with the landfalling TC (LTC) frequency over China in the following summer. After removing the El Niño–Southern Oscillation (ENSO) signal, there still exists a significant positive correlation between them. Observational evidence and numerical model experiments consistently confirm that this time-lagged association is attributable to the air–sea interaction processes in the tropical Pacific. Thus, the results of this study could provide an additional predictor besides ENSO to improve understanding of the LTC activity in China.

Restricted access
Jiali Wang
,
Georgios Deskos
,
William J. Pringle
,
Sue Ellen Haupt
,
Sha Feng
,
Larry K. Berg
,
Matt Churchfield
,
Mrinal Biswas
,
Walter Musial
,
Paytsar Muradyan
,
Eric Hendricks
,
Rao Kotamarthi
,
Pengfei Xue
,
Christopher M. Rozoff
, and
George Bryan
Open access
Huancui Hu
,
L. Ruby Leung
,
Zhe Feng
, and
James Marquis

Abstract

Moisture recycling, the contribution of local evapotranspiration (ET) to precipitation, has been studied using bulk models assuming a well-mixed atmosphere. The latter is inconsistent with a climatologically stratified atmosphere that slants across latitudes. Reconciling the two views requires an understanding of overturning associated with different weather systems. In this study, we aim to better understand moisture recycling associated with mesoscale convective systems (MCSs). Using a convection-permitting WRF simulation equipped with water vapor tracers (WRF-WVT), we tag moisture from terrestrial ET in the U.S. Southern Great Plains during May 2015, when more than 20 MCS events occurred and produced significant precipitation and flooding. Water budget analysis reveals that approximately 76% of terrestrial ET is advected away from the region while the remaining 24% of terrestrial ET is “pumped” upward within the region, accounting for 12% of precipitation. Moisture recycling peaks during early night hours (1800–2400 LT) due to the mixing of the daytime accumulated ET by active convection. By focusing on five “diurnally driven” MCSs with less large-scale circulation influence than other MCSs during the same period, we find an upright pumping of terrestrial ET at the MCS initiation and development stages, which diverges into two branches during the MCS mature and decaying stages. One branch in the upper level advects the ET-sourced moisture downstream, while the other branch in the mid-to-upper level contributes to the trailing precipitation upstream. Overall, our analysis depicts a pumping mechanism associated with MCSs that mixes local ET vertically, highlighting its specific contributions to enhancing convective precipitation processes.

Restricted access
Chin-Hsuan Peng
and
Xingchao Chen

Abstract

Previous observational studies have indicated that mesoscale convective systems (MCSs) contribute the majority of precipitation over the Bay of Bengal (BoB) during the summer monsoon season, yet their initiation and propagation remain incompletely understood. To fill this knowledge gap, we conducted a comprehensive study using a combination of 20-year satellite observations, MCS tracking, reanalysis data, and a theoretical linear model. Satellite observations reveal clear diurnal propagation signals of MCS initiation frequency and rainfall from the west coast of the BoB toward the central BoB, with the MCS rainfall propagating slightly slower than the MCS initiation frequency. Global reanalysis data indicates a strong association between the offshore-propagating MCS initiation frequency/rainfall and diurnal low-level wind perturbations, implying the potential role of gravity waves. To verify the hypothesis, we developed a 2-D linear model that can be driven by realistic meteorological fields from reanalysis. The linear model realistically reproduces the characteristics of offshore-propagating diurnal wind perturbations. The wind perturbations, as well as the offshore propagation signals of MCS initiation frequency and rainfall, are associated with diurnal gravity waves emitted from the coastal regions, which in turn are caused by the diurnal land-sea thermal contrast. The ambient wind speed and vertical wind shear play crucial roles in modulating the timing, propagation, and amplitude of diurnal gravity waves. Using the linear model and satellite observations, we further show that the stronger monsoonal flows lead to faster offshore propagation of diurnal gravity waves, which subsequently control the offshore propagation signals of MCS initiation and rainfall.

Restricted access