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  Subjects -> METEOROLOGY (Total: 106 journals)
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Climate Dynamics
Journal Prestige (SJR): 2.445
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1432-0894 - ISSN (Online) 0930-7575
Published by Springer-Verlag Homepage  [2468 journals]
  • Three types of East Asian summer rainfall associated with monsoon
           circulation and tropical cyclone activities: unique features and major
           influential factors

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      Abstract: Abstract Most previous studies have investigated East Asian summer rainfall as one element. This study investigates the East Asian summer monsoon (EASM), Western North Pacific (WNP) tropical cyclones (TCs), and the concurrent rainfall occurring between May and September from 1983 to 2021. Three distinct types of rainfall are identified: monsoon-only rainfall, TC-only rainfall, and monsoon-TC joint rainfall (MS-TC rainfall), each exhibiting its own unique characteristics. Monsoon-only rainfall is characterized by positive anomalies along the East Asian subtropical front, while a decrease in TC activity leads to negative rainfall anomalies in the tropical WNP. TC-only rainfall, on the other hand, contributes to positive rainfall anomalies in the tropical WNP, as more TCs exhibit westward movement. In the case of MS-TC rainfall, positive precipitation anomalies are observed in the Philippines, the Korean Peninsula, and southern Japan. These anomalies can be attributed to an enhanced northward movement of TCs during such rainfall events. During strong monsoon-only (TC-only) rainfall years, the tropical western Pacific experiences anticyclonic (cyclonic) anomalies, along with a westward (eastward) shift of monsoon trough and WNP subtropical high (WNPSH). In strong MS-TC years, a localized cyclonic anomaly dominates the Philippine Basin, resulting in an eastward shift of the monsoon trough and WNPSH. Additionally, a significant increase (decrease) in vertical wind shear (VWS) is observed in the tropical WNP during strong monsoon-only (TC-only) years, while a moderate decrease is observed in strong MS-TC years. Distinct influential factors are associated with each rainfall type. Preceding positive sea surface temperature (SST) anomalies in the offshore China seas and WNP, in conjunction with the El Niño-Southern Oscillation (ENSO), play a primary role in driving interannual variations of monsoon-only rainfall. ENSO serves as the principal modulator of interannual variations in TC-only rainfall. Additionally, anomalous thermal conditions in the Maritime Continent (MC) act as major drivers for MS-TC rainfall. This study enhances our understanding of the underlying mechanisms and influential factors contributing to the diverse patterns of East Asian summer rainfall.
      PubDate: 2024-02-23
       
  • Low-wind climatology (1979–2018) over Europe from ERA5 reanalysis

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      Abstract: Abstract Research on wind speed characteristics is of interest for many disciplines from renewable energy to ecology. Whereas mean values and trends are commonly studied, less attentions is paid to the evaluation of other features such as low-wind conditions. However, there is no clear definition of “low-wind” on the literature. Here we propose the Beaufort scale to characterize low-wind values over Europe through a fixed threshold of 3.3 m/s (“light breeze" category). Climatological (1979–2018) assessment is performed using ERA5 reanalysis hourly data. The limited amount of observational stations indicate a 40-year averaged amount of around 3500 low-wind hours/year, comparable to the corresponding ERA5 reanalysis cells, which shows severe limitations over mountainous areas. The European domain features a strong north–south low-wind hours gradient. Remarkable patterns are obtained over coasts and complex orography regions. Seasonal low-wind variability range around 20–25% for most of the regions, and interannual coefficient of variability from 0.05 to 0.17. Oceanic regions present smaller low-wind values than land areas, with Atlantic and Mediterranean regions behaving differently. The largest annual spells (consecutive) hourly low-wind episodes are within the range from 5 to 10 days, (from 120 to 240 h) over many land areas. Annual mean hourly wind spells typically extend from 15 to 25 h, with more than 200 episodes.
      PubDate: 2024-02-23
       
  • Physical understanding of the tropical cyclone intensity and size
           relations over the North Indian Ocean

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      Abstract: Abstract Tropical cyclone (TC) size and intensity define the potential destructiveness in the land-falling region. This study investigates the inter-relationships between size parameters (radius of maximum wind, Rmax; 34-knots wind, R34; and TC-fullness, TCF) and intensity. The best-track (size and intensity) data is obtained from the Joint Typhoon Warning Center during 2002–2021. The frequently observed R34, Rmax, and TCF are 100–150 km, 20–60 km, and 0.8, respectively for NIO TCs. Intensity and TCF are more strongly related (0.7) than R34 (0.5) and Rmax (0.6). Analysis shows that size changes are weakly related to intensity changes (0.37–0.39). Diagnostic analysis has been conducted to address possible reasons for different TC groups 1) TCs with no size variation with intensity (Group-1), (2) both increase (Group-2), (3) size increases with no intensity change (Group-3), (4) Initial more size (Group-4). The dry air intrusion outside the eyewall in Group-1 TCs in low vertical wind shear condition limit rain-bands development, enabling moisture convergence into the primary eyewall that helps maintain storm intensity without R34 increase. Strong surface fluxes in the primary eyewall region support convection and absolute angular momentum (AAM) at upper and lower levels, which boosts size and intensity in Group-2 TCs. Strong and broader surface fluxes and vertical velocities may create rain-bands or secondary-eyewall, causing bigger TCs with limited intensification in Group-3 TCs. Larger initial TC vortices maintain wider and intense surface fluxes, vertical velocities, and AAM in the TC inner and outer cores, supporting the maintenance of larger TC size in Group-4.
      PubDate: 2024-02-22
       
  • On the impact of net-zero forcing Q-flux change

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      Abstract: Abstract Numerical climate model simulations suggest that global warming is enhanced or hampered by the spatial pattern of the warming itself. This phenomenon is known as the “pattern effect” and has in recent years become the most promising explanation for the change over time of climate sensitivity in climate models. Under historical global warming, different patterns of surface-temperature change have emerged, notably a yet unexplained cooling in the Southern Ocean and the East Pacific. Historical climate model simulations notoriously fail to reproduce this cooling, which may contribute to the deviation of the simulated global-mean warming from the observed record. Here we qualitatively investigate the potential impact of historical and other surface-temperature pattern changes by changing the ocean heat transport convergence (Q-flux) in a slab-ocean model. The Q-flux changes are always implemented such that in the global mean they impose no net forcing. Consistent with earlier studies we find that the impact of a negative Q-flux change in the Southern Ocean has a stronger effect than in other regions because of a feedback loop between sea-surface temperatures (SSTs) and clouds in the Southern Ocean and the stably stratified regions in the tropics. The SST-cloud feedback loop facilitates the expansion of the Antarctic sea ice, indeed taking the model into a Snowball-Earth state. The intensity of this effect is found to be model dependent, especially due to differences in the cloud parametrisation. In experiments with deactivated sea ice the impact of the negative Q-flux change is much weaker.
      PubDate: 2024-02-22
       
  • Defining a Caribbean regional-scale mid-summer drought based on weather
           types from 1950 to 2021

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      Abstract: Abstract The detection and the functioning of the mid-summer drought (MSD) represent valuable information due to its socio-economic implications for the Caribbean. Current methods using local-scale rainfall to define the MSD have some limitations. This paper presents a novel approach to detect MSD from regional-scale weather types (WT). Long sequences of a typical summertime anticyclonic WT allow the detection of the onset and demise dates of the MSD for most years in 1950–2021. The MSD defined with WT (MSD-WT) begins rather abruptly on June 13th and concludes on August 21st, on average. While the interannual variations of the MSD-WT onset are relatively weak, long-term trends since 1950 indicate progressive earlier onsets, longer durations, and weakening intensities of the MSD-WT. Our results do not show the anticipated westward shift of the North Atlantic subtropical high pressure typically related to MSD. Instead, they indicate a halt of its eastward shift close to the MSD-WT onset. The absence of significant correlations between MSD-WT onset and either the Tropical North Atlantic or the Eastern Tropical Pacific sea surface temperature (SST) in May–June also suggests a mostly intrinsic atmospheric mechanism locked to the annual cycle, thus limiting the seasonal predictability of the MSD-WT onset. Furthermore, our results indicate a lag between the timing of increased subsidence, acceleration of the Caribbean low-level jet (CLLJ), and intensification of the deep convection over Central America and Mexico. This leads us to develop a novel hypothesis putting forward the monsoon circulation over Meso-America as a potential precursor of the increased subsidence over the Caribbean basin and the synchronous acceleration of CLLJ. The MSD-WT demise is more gradual and corresponds to a decrease in regional-scale mean sea level pressure and a weakening of the CLLJ. MSD-WT demise dates exhibit also relatively larger interannual variations but, unlike its onset, do not show any significant long-term trend. Anomalously warm (cold) Tropical North Atlantic and cold (warm) East Pacific SST from early June are correlated with an earlier (later) MSD-WT demise than usual. MSD-WT demise seems to involve regional-scale air-sea couplings and exhibits thus more seasonal predictability. Finally, despite a consistent response to the CLLJ, distinct processes seem to produce the relatively dry conditions observed over the Pacific coast of Central America and the Caribbean basin during the MSD.
      PubDate: 2024-02-21
       
  • Interannual variability of diurnal temperature range in CMIP6 projections
           and the connection with large-scale circulation

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      Abstract: Abstract Diurnal temperature range (DTR), as a core indicator of the Earth system, exhibits obvious temporal and spatial variations, which is not entirely consistent over global. The historical simulation capabilities of 19 Coupled Model Intercomparison Project 6 (CMIP6) models for DTR were firstly evaluated against CRU_TS v4.04 data. Future changes under three shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, SSP5-8.5) in DTR were projected using a multi-model ensemble mean (MME), and its interannual variations were seasonally explored through empirical orthogonal function (EOF) analysis. The results indicated that CMIP6 models could reflect the decreasing trend of DTR during 1901–2014, with the global spatial correlation coefficient between models and observation ranging from 0.4 to 0.7. MME outperformed individual models in both spatial and temporal variations, indicating higher accuracy and reliability. The future changes of DTR exhibited significantly decrease across the northern hemisphere and increase in the South America, and change magnitude enlarged with time extension and emission intensity, especially by more than 0.4 °C under SSP5-8.5. The decreasing trend of global DTR was kept in SSP2-4.5 and SSP5-8.5, while SSP1-2.6 changed increasing trend during 2015–2100. DTR showed seasonal variations and was mainly influenced by colder months. The dominant modes of interannual DTR and their relationship with the 500 hPa geopotential height, the 200 hPa U wind, and the outgoing longwave radiation showed higher features in tropical regions. The highly positive correlation between the first mode of DTR and the Niño3.4 index in December/January/February (DJF) is 0.67, indicating significant influence of the El Niño-Southern Oscillation on DTR.
      PubDate: 2024-02-21
       
  • Correction: Skill decreases in real-time seasonal climate prediction due
           to decadal variability

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      PubDate: 2024-02-20
       
  • Understanding of CMIP6 surface temperature cold bias over the westerly and
           monsoon regions of the Tibetan Plateau

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      Abstract: Abstract The Tibetan Plateau (TP) directly heats the middle tropospheric atmosphere, and accurate simulation of its surface temperature is of great concern for improving climatic prediction and projection capabilities, but climate models always exhibit a cold bias. Based on the Coupled Model Intercomparison Project Phase 6 (CMIP6) models and in-situ observations during 1981–2014, this study elucidates the impact of the snow overestimation on the temperature simulation over the TP in CMIP6 from the perspective of local radiation processes and atmospheric circulation. On the one hand, more snow in the CMIP6 models not only directly cools the surface more, but also makes the surface receive less shortwave radiation due to the higher surface albedo, and thus has lower ground surface temperature (GST), and the more snow/albedo-low temperature process is particularly evident in the westerly region due to more uncertainty at high elevations. This process contributes 87% to the annual GST cold bias. Lower GST corresponds to less latent heat transfer and thereby lower surface air temperature (SAT). In addition, the more snow in the CMIP6 models leads to the weaker the South Asian summer monsoon and the westerlies, and brings less warm and moist air (less integrated water vapor flux), as well as less clear-sky downward longwave radiation (less water vapor amount and lower tropospheric air temperature) to the TP (contributing 58% to the annual GST cold bias). These processes will result in less both precipitation and surface latent heat loss, which offsets a 35% annual GST cold bias. Besides, the physical mechanism of snow on GST and SAT differs with season over the westerly and monsoon regions of the TP. The research highlights the importance of topography and snow parameterization schemes for optimizing CMIP6 models.
      PubDate: 2024-02-20
       
  • Interdecadal variation of tropical cyclone genesis longitudes over the
           western North Pacific

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      Abstract: Abstract Statistical change-point analysis was used to examine a significant change in the average longitude locations of tropical cyclone (TC) genesis from June to October between 1979 and 2020. It was observed that since 1998, the TC genesis location has shifted westward. This study investigates the causes of this interdecadal shift in the western North Pacific (WNP). During the recent period (1998–2020), a westward shift was noted in precipitation, outgoing longwave radiation, precipitable water, and total cloud cover. The primary driver for this shift is the negative phase of the Pacific Decadal Oscillation during the second period. A positive sea surface temperature (SST) anomaly enhances convection over the South China Sea and adjacent waters west of 140° E, which retreats the monsoon trough toward the west. Furthermore, the Rossby wave response to a negative SST anomaly over the central and eastern Pacific causes the WNP subtropical high in the lower troposphere to move further west, pushing the monsoon trough in the same direction. The westward shifts in convection and circulation are maintained by a strengthened Walker circulation.
      PubDate: 2024-02-17
       
  • Mesoscale anomalous three-dimensional atmospheric circulation underpinned
           regional heavy rainfall events in the eastern foot of Tibetan Plateau

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      Abstract: Abstract Based on hourly ERA5 reanalysis and station rainfall data of China, this study investigated the mesoscale anomalous atmospheric circulation linked with heavy rainfall events around Yaan China. Yaan located in steep terrain on the eastern foot of Tibetan Plateau and is in the trumpet corner region of western Sichuan Basin of China. Yaan areas serve as a regional heavy rainfall center. Analysis revealed that the principal atmospheric circulation features, which underpin heavy rainfall, is probably a mesoscale (within 500 km) anomalous circulation system characterized by anomalous upper tropospheric warming (around 300–500 hPa) and lower stratospheric cooling (around 100 hPa) above Yaan, which against large-scale upper tropospheric backgrounds either warm or cold over East China. The anomalous temperature pattern corresponds to a positive (negative) geopotential height anomaly and mesoscale divergence (convergence) at 150–200 hPa (800–925 Pa). The anomalous low-level easterly winds blowing towards the steep terrain, together with the upper-level divergence, favor the occurrence of heavy rainfall around Yaan. The formation of the mesoscale upper-level warm anomaly over Yaan under a large-scale cold background could be contributed by the interaction between the stratosphere and troposphere, the transport of warm air mass from the northern Tibetan Plateau in the upper troposphere and also the match of middle-lower tropospheric warm anomalies jointly. The findings of this study highlight the importance of the influence of upper-tropospheric mesoscale circulations to heavy rainfall.
      PubDate: 2024-02-16
       
  • Thermodynamic characteristics of extreme heat waves over the middle and
           lower reaches of the Yangtze River Basin

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      Abstract: Abstract In August 2022, an exceptionally long-lasting heat wave (HW) affected the middle and lower reaches of the Yangtze River basin. This study uses the JRA55 daily reanalysis datasets to elucidate the thermodynamic characteristics of the daily evolution of historical extreme HWs in this region via the heat budget equation. HWs are generally characterized by the occurrence of anticyclonic circulation anomaly throughout the troposphere and positive air temperature anomaly with the maximum amplitude in the boundary layer. The anticyclonic anomaly can induce compression heating in the entire troposphere and warm zonal advection in the boundary layer. Meanwhile, due to the reduced cloud cover, more shortwave radiation reaches the ground surface, and the sensible heat flux becomes an important source of diabatic heating before the onset of HWs. The accumulated excessive heat in the HWs is primarily damped through the emission of longwave radiation and meridional thermal advection. For the HW in August 2022, its extreme persistence is mainly caused by prolonged adiabatic heating, enhanced diabatic heating during the developing stage and weakened diabatic cooling during the decay stage. The upper-level portion of the anticyclonic circulation anomalies is linked to the strengthened South Asia High. After applying the state-of-the-art dynamic metric, i.e., local finite wave activity, we reveal that the formation of the anomalous South Asia High in August 2022 is associated with the Stokes drift flux rather than the dispersion of Rossby wave energy. This characteristic sets it apart from other extreme HWs.
      PubDate: 2024-02-14
       
  • Sensitivity of PBL parameterization schemes in simulating lightning and
           thunderstorm using WRF-ELEC model

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      Abstract: Abstract Climate change’s impact on lightning and thunderstorms is uncertain. This study evaluates the sensitivity of multiple Planetary Boundary Layer (PBL) parameterisation schemes within the WRF-ELEC model for simulating a severe lightning and thunderstorm event in Bihar on 25 June 2020. The aim is to understand how these schemes affect lightning and thunderstorm intensity. The model was integrated for 54 h at 0000 UTC on 24 June 2020 using 6-hourly NCEP FNL Operational Global Analysis data at 1° × 1° resolution over Bihar with double nested domains of 9 km (D1) and 3 km (D2). It effectively captures the peak lightning and thunderstorm activity from 0000 to 0900 UTC on 25 June 2020, significantly impacting certain regions. The study utilised ERA5 and IMDAA reanalysis datasets and NASA GPM IMERG daily data to analyse the event and assess the model’s performance. Among the PBL schemes tested, ACM2, BouLac, SHsa, and MRF exhibit robust performance. Flash Origin Density (FOD) patterns broadly match observations, although occasional discrepancies occur in southern Bihar. Convective Available Potential Energy (CAPE) and precipitation (mm) analysis reveals anticipated trends. Statistical scores highlight strong performance by ACM2, UW, and GBM schemes in POFD/FAR. The MRF scheme excels in POD/Hit Rate, and the UW scheme achieves the highest score for 24-h accumulated total precipitation. HSS and GSS/ETS underscore the superior performance of the UW and GBM schemes. This study offers insights into lightning and thunderstorm simulations over Bihar with diverse PBL parameterisation schemes in the WRF-ELEC model.
      PubDate: 2024-02-13
       
  • Interannual variability of mid-high-latitude intraseasonal oscillation
           intensity at the southern hemisphere during austral summer

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      Abstract: Abstract The interannual variation of intraseasonal (10–30-day) oscillation (ISO) intensity for the eastward- and westward- propagating types over the mid-high latitudes in austral summer is studied. It indicates that during strong ISO years, the wave train has a larger amplitude and wider zonal influencing range. The wave train propagates eastward in both strong and weak eastward-propagating ISO years, while it propagates westward only in strong westward-propagating ISO years. One possible explanation for the larger magnitude of the wave train in strong ISO years is that the ISO perturbation acquires more energy from the mean flow through the barotropic kinetic energy and potential energy conversion. Based on the diagnostic results of the geopotential height trend, the maximum contributor to the eastward propagation is the same during strong and weak ISO years, as well as for the westward propagation. However, the relative contribution of the relative vorticity’s meridional advection in weak years is smaller than that in strong years, which may be the reason why there is no significant westward propagation in weak ISO years. Due to the difference in amplitude and influencing range of the wave train during strong and weak ISO years, the two ISO types have different effects on the surface air temperate over land areas at the Southern Hemisphere. The interannual variation of the eastward-propagating ISO intensity appears to be linked to the El Niño-Southern Oscillation and Southern Annular Mode, while the westward-propagating ISO appears unrelated to them.
      PubDate: 2024-02-11
       
  • Correction: A multiple linear regression model for the prediction of
           summer rainfall in the northwestern Peruvian Amazon using large-scale
           indices

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      PubDate: 2024-02-09
       
  • Exploring warm extremes in South America: insights into regional climate
           change projections through dry-bulb and wet-bulb temperatures

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      Abstract: Abstract This study addresses a regional research gap by analyzing summertime wet-bulb temperature (Tw) projections in South America (SA) and their implications for heatwaves in central-east Argentina (CEA). Tw emerges as a relevant variable to address the potential impact of humid and warm extremes under future climate conditions, while allowing comparison with more classical analyses based on dry-bulb temperature indices. The analyses presented in this work are based on outputs from Regional Climate Models provided by CORDEX (COordinated Regional climate Downscaling EXperiment) South America database. Tw increases in all SA stem from rising temperature and specific humidity at lower atmospheric layers. Projected Tw rise surpasses the expected maximum dry-bulb temperature (Tmax) increase across most of SA, exhibiting pronounced disparities in subtropical areas and intensifying further in CEA towards the century’s end. Projected trends in Tw and minimum dry-bulb temperature (Tmin) show similarities across SA, except for a limited area within CEA where relatively larger Tw increases are expected. The frequency and intensity of heat extremes are also anticipated to increase in the coming years in SA. Noteworthy findings encompass projected increases in hot days, hot nights, and wet days, with the tropical region standing out for its pronounced projections. Remarkably, the number of wet days would rise significantly, followed by less prominent increases in the number of hot nights and days. Moreover, heightened persistence is expected for wet days compared to hot days and nights. A bivariate statistical analysis of heatwave projections in CEA reveals a transition towards warmer and more humid spells. This underscores the critical need to integrate air humidity conditions for accurate assessments of future health risks. Despite inherent uncertainties in climate change projections, consensus emerges on the direction of the expected changes, as well as on the urgency of limiting greenhouse gas emissions to mitigate the imminent threat of humid heatwaves in CEA.
      PubDate: 2024-02-09
       
  • Formation of long-lasting inactive and active multiple tropical cyclone
           events in the western North Pacific

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      Abstract: Abstract Long-lasting inactive and active multiple tropical cyclone (MTC) events in the western North Pacific (WNP) during July–August 1982–2020 were investigated. It is found that the significant difference between the inactive and active events lies on large-scale circulation conditions and tropical SST anomalies in the Pacific and Indian Ocean. A negative phase of the Pacific Meridional Mode (PMM), an Indian ocean warming and a local suppressed convective phase are associated with the long-lasting inactive MTC events, and vice versa. A further diagnosis of the environmental parameters showed that dynamic parameters such as mid-level vertical motion and the upper-level divergence and thermodynamic parameters such as vertically integrated water vapor content and low-level specific humidity play important roles in regulating the inactive and active MTC events. A separation of interannual and intraseasonal components indicates that the extreme MTC events are influenced by both the timescale motions. While the former is primarily through the SSTA-induced low-level anticyclonic and descent anomalies, the latter is via the fluctuation of the boreal summer atmospheric intraseasonal oscillation.
      PubDate: 2024-02-08
       
  • Drivers of coupled climate model biases in representing Labrador Sea
           convection

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      Abstract: Abstract This study investigates the representation of ocean convection in the Labrador Sea in seven Earth System Models (ESMs) from the Coupled Model Intercomparison Project Phase 5 and 6 datasets. The relative role of the oceanic and atmospheric biases in the subpolar North Atlantic gyre are explored using regional ocean simulations where the atmospheric forcing or the ocean initial and boundary conditions are replaced by reanalysis data in the absence of interactive air-sea coupling. Commonalities and differences among model behaviors are discussed with the objective of finding a pathway forward to improve the representation of the ocean mean state and variability in a region of fundamental importance for climate variability and change. Results highlight that an improved representation of ocean stratification in the North Atlantic subpolar gyre is urgently needed to constrain future climate change projections. While improving the ocean model resolution in the North Atlantic alone may contribute a better representation of both boundary currents and propagation of heat and freshwater anomalies into the Labrador Sea, it may not be sufficient. Addressing the atmospheric heat flux bias with better resolution in the atmosphere and land topography may allow for deep convection to occur in the Labrador Sea in some of the models that miss it entirely, but the greatest priority remains improving the representation of ocean stratification.
      PubDate: 2024-02-07
       
  • The sensitivity of the North American Monsoon to Gulf of California Sea
           surface temperatures

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      Abstract: Abstract The sensitivity of North American Monsoon rainfall to sea surface temperatures (SST) in the Gulf of California (GoC) is assessed using a set of convection-permitting regional climate models. Simulations are performed from May through September 1994 and consist of one control run and two experimental runs that positively and negatively perturb SSTs exclusively within the GoC. Averaged across the season, rainfall increases by 23% in response to spatial mean warming of 1.4 K for the GoC. The direct conversion of GoC moisture into precipitation accounts for 19% of this total increase in rainfall. Increases in rainfall early in the season are more strongly supported by changes in mean thermodynamics that favor stronger moisture flux convergence. Additionally, enhanced inland moisture transport from the GoC increases the amount of convective available potential energy across the region and allows for stronger vertical convective fluxes that intensifies precipitation. A secondary mean circulation response also favors greater precipitation and is related to the advection of cooler air off the mountains of the Sierre Madre Occidental over the GoC. This cooler air mass lowers geopotential heights and drives a cyclonic wind anomaly that favors enhanced flow from the GoC towards the Sierre Madre Occidental mountain range. Later in the season, comparatively smaller increases in rainfall are attributed to increases in local terrestrial evaporation that serve as a positive feedback to initial increases in rainfall driven by perturbed SSTs.
      PubDate: 2024-02-07
       
  • SPEEDY-NEMO: performance and applications of a fully-coupled
           intermediate-complexity climate model

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      Abstract: Abstract A fully-coupled general circulation model of intermediate complexity is documented. The study presents an overview of the model climatology and variability, with particular attention to the phenomenology of processes that are relevant for the predictability of the climate system on seasonal-to-decadal time-scales. It is shown that the model can realistically simulate the general circulation of the atmosphere and the ocean, as well as the major modes of climate variability on the examined time-scales: e.g. El Niño-Southern Oscillation, North Atlantic Oscillation, Tropical Atlantic Variability, Pacific Decadal Variability, Atlantic Multi-decadal Variability. Potential applications of the model are discussed, with emphasis on the possibility of generating sets of low-cost large-ensemble retrospective forecasts. We argue that the presented model is suitable to be employed in traditional and innovative model experiments that can play a significant role in future developments of seasonal-to-decadal climate prediction.
      PubDate: 2024-02-07
       
  • Representing rainfall extremes over the Indo-Gangetic Plains using
           CORDEX-CORE simulations

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      Abstract: Abstract The Indo-Gangetic Plain (IGP), which is the site of India's Green Revolution, covers almost 15% of the country's landmass and is among the most extensively fertile lands across the world. The densely populated IGP region bears great importance for the socioeconomic facets of India and contributes to a major share of the GDP of the country. The present study demonstrates the regional-specific assessment of summer monsoon precipitation and associated extremes with dynamical and thermodynamical aspects over the IGP region using high-resolution regional climate models (RCMs) under the CORDEX-CORE framework. The analysis reveals that the eastern parts of the IGP receive low-to-moderate precipitation with a higher tail than the western parts, which is due to the direction of the monsoon low-level flow. The observed mean precipitation characteristics are well represented by the RCMs. Further, the research identifies extreme precipitation events over the IGP and conducts comprehensive analysis to understand their underlying mechanisms. It has been observed that extreme precipitation events are linked with the moisture transport associated with trough activity and instability, and RCMs are capable in representing the observed precipitation extremes and underlying mechanisms at localized scales. Overall, this study represents a significant step forward in understanding the evolution of spatio-temporal variability of precipitation over the IGP region, where agriculture is a major economic activity and millions of people depend on rainfed agriculture.
      PubDate: 2024-02-07
       
 
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