scholarly journals A Comparison of Three Prolonged Periods of Heavy Rainfall over the Hawaiian Islands

2012 ◽  
Vol 51 (4) ◽  
pp. 722-744 ◽  
Author(s):  
I. M. Shiromani Jayawardena ◽  
Yi-Leng Chen ◽  
Andrew J. Nash ◽  
Kevin Kodama
Keyword(s):  
Heavy Rainfall ◽  
Large Scale ◽  
Hawaiian Islands ◽  
Hadley Circulation ◽  
Wind Component ◽  
Central Pacific ◽  
Optimal Position ◽  
Subtropical Jet ◽  
Circulation Patterns ◽  
Stormy Weather

AbstractThe anomalous circulation patterns during an unusually prolonged stormy-weather period in Hawaii from 19 February to 2 April 2006 are analyzed and are compared with those of two previously known prolonged heavy-rainfall periods (March 1951 and February 1979). The circulation patterns for these three periods are characterized by 1) a negative Pacific–North American (PNA) pattern in the midlatitudes with a blocking high southwest of the Aleutian Islands, 2) retraction and splitting of the zonal jet into a polar jet north of 50°N and a persistent subtropical jet to the south over the central Pacific Ocean, 3) an anomalous low west of the Hawaiian Islands embedded in the subtropical jet, and 4) a weaker-than-normal Hadley circulation in the mid-Pacific. The moisture advected from low latitudes by the southerly wind component east of the persistent anomalous low, combined with upward motion, provides the large-scale setting for the unusually prolonged unsettled weather across the Hawaiian Islands. For all three cases, the prolonged stormy weather started after the onset of large-scale blocking and a negative PNA pattern over the North Pacific and the occurrence of a persistent anomalous low embedded in the subtropical jet west of the Hawaiian Islands. Furthermore, the persistent low was located at the optimal position to bring moisture from the central equatorial Pacific to Hawaii. The stormy weather ceased after the midlatitude blocking pattern weakened and the anomalous low in the subtropics decayed and/or shifted westward. There are no apparent common precursors in the 2-week period prior to the prolonged stormy weather among these three cases, however.

scholarly journals Western U.S. lake expansions during Heinrich stadials linked to Pacific Hadley circulation

2018 ◽  
Vol 4 (11) ◽  
pp. eaav0118 ◽  
Author(s):  
D. McGee ◽  
E. Moreno-Chamarro ◽  
J. Marshall ◽  
E. D. Galbraith
Keyword(s):  
United States ◽  
Hadley Circulation ◽  
Winter Precipitation ◽  
Aleutian Low ◽  
Central Pacific ◽  
Subtropical Jet ◽  
Precipitation Anomalies ◽  
Hemisphere Winter ◽  
Atmospheric Changes ◽  
Precipitation Changes

Lake and cave records show that winter precipitation in the southwestern United States increased substantially during millennial-scale periods of Northern Hemisphere winter cooling known as Heinrich stadials. However, previous work has not produced a clear picture of the atmospheric circulation changes driving these precipitation increases. Here, we combine data with model simulations to show that maximum winter precipitation anomalies were related to an intensified subtropical jet and a deepened, southeastward-shifted Aleutian Low, which together increased atmospheric river–like transport of subtropical moisture into the western United States. The jet and Aleutian Low changes are tied to the southward displacement of the intertropical convergence zone and the accompanying intensification of the Hadley circulation in the central Pacific. These results refine our understanding of atmospheric changes accompanying Heinrich stadials and highlight the need for accurate representations of tropical-extratropical teleconnections in simulations of past and future precipitation changes in the region.

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

scholarly journals Subseasonal Forecasts of the Northern Queensland Floods of February 2019: Causes and Forecast Evaluation

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 758
Author(s):  
Wayne Yuan-Huai Tsai ◽  
Mong-Ming Lu ◽  
Chung-Hsiung Sui ◽  
Yin-Min Cho
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Austral Summer ◽  
Rainfall Event ◽  
Monsoon Depression ◽  
Forecast Skill ◽  
Sea Surface ◽  
Central Pacific ◽  
Percentile Rank ◽  
Extended Range

During the austral summer 2018/19, devastating floods occurred over northeast Australia that killed approximately 625,000 head of cattle and inundated over 3000 homes in Townsville. In this paper, the disastrous event was identified as a record-breaking subseasonal peak rainfall event (SPRE). The SPRE was mainly induced by an anomalously strong monsoon depression that was modulated by the convective phases of an MJO and an equatorial Rossby (ER) wave. The ER wave originated from an active equatorial deep convection associated with the El Niño warm sea surface temperatures near the dateline over the central Pacific. Based on the S2S Project Database, we analyzed the extended-range forecast skill of the SPRE from two different perspectives, the monsoon depression represented by an 850-hPa wind shear index and the 15-day accumulated precipitation characterized by the percentile rank (PR) and the ratio to the three-month seasonal (DJF) totals. The results of four S2S models of this study suggest that the monsoon depression can maintain the same level of skill as the short-range (3 days) forecast up to 8–10 days. For precipitation parameters, the conclusions are similar to the monsoon depression. For the 2019 northern Queensland SPRE, the model forecast was, in general, worse than the expectation derived from the hindcast analysis. The clear modulation of the ER wave that enhanced the SPRE monsoon depression circulation and precipitation is suspected as the main cause for the lower forecast skill. The analysis procedure proposed in this study can be applied to analyze the SPREs and their associated large-scale drivers in other regions.

scholarly journals A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 914
Author(s):  
Tao Chen ◽  
Da-Lin Zhang
Keyword(s):  
South China ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Convective Available Potential Energy ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Precipitable Water ◽  
Atmospheric Parameter ◽  
Low Level ◽  
Warm Sector

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China.

Changes of South‐Central Pacific Large‐Scale Environment Associated With Hydrometeors‐Radiation‐Circulation Interactions in a Coupled GCM

2021 ◽  
Vol 126 (17) ◽  
Author(s):  
J.‐L. F. Li ◽  
Kuan‐Man Xu ◽  
Wei‐Liang Lee ◽  
J. H. Jiang ◽  
Eric Fetzer ◽  
...  
Keyword(s):  
Large Scale ◽  
Central Pacific ◽  
Coupled Gcm ◽  
South Central

Six-fold increase in historical Northern Hemisphere concurrent large heatwaves driven by warming and changing atmospheric circulations

2021 ◽  
pp. 1-39
Author(s):  
Cassandra D.W. Rogers ◽  
Kai Kornhuber ◽  
Sarah E. Perkins-Kirkpatrick ◽  
Paul C. Loikith ◽  
Deepti Singh
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Warm Season ◽  
Fold Increase ◽  
Circulation Pattern ◽  
Positive Influence ◽  
Climate Risks ◽  
Circulation Patterns ◽  
Multiple Regions ◽  
Barents And Kara Seas

AbstractSimultaneous heatwaves affecting multiple regions (referred to as concurrent heatwaves), pose compounding threats to various natural and societal systems, including global food chains, emergency response systems, and reinsurance industries. While anthropogenic climate change is increasing heatwave risks across most regions, the interactions between warming and circulation changes that yield concurrent heatwaves remain understudied. Here, we quantify historical (1979-2019) trends in concurrent heatwaves during the warm-season (May-September, MJJAS) across the Northern Hemisphere mid- to high-latitudes. We find a significant increase of ~46% in the mean spatial extent of concurrent heatwaves, ~17% increase in their maximum intensity, and ~6-fold increase in their frequency. Using Self-Organising Maps, we identify large-scale circulation patterns (300 hPa) associated with specific concurrent heatwave configurations across Northern Hemisphere regions. We show that observed changes in the frequency of specific circulation patterns preferentially increase the risk of concurrent heatwaves across particular regions. Patterns linking concurrent heatwaves across eastern North America, eastern and northern Europe, parts of Asia, and the Barents and Kara Seas, show the largest increases in frequency (~5.9 additional days per decade). We also quantify the relative contributions of circulation pattern changes and warming to overall observed concurrent heatwave day frequency trends. While warming has a predominant and positive influence on increasing concurrent heatwaves, circulation pattern changes have a varying influence and account for up to 0.8 additional concurrent heatwave days per decade. Identifying regions with an elevated risk of concurrent heatwaves and understanding their drivers is indispensable for evaluating projected climate risks on interconnected societal systems and fostering regional preparedness in a changing climate.

scholarly journals Austral Spring Stratospheric and Tropospheric Circulation Interannual Variability

2011 ◽  
Vol 24 (11) ◽  
pp. 2629-2647 ◽  
Author(s):  
Eduardo Andrés Agosta ◽  
Pablo Osvaldo Canziani
Keyword(s):  
Interannual Variability ◽  
High Index ◽  
Stationary Waves ◽  
Energy Propagation ◽  
Central Pacific ◽  
Austral Spring ◽  
Circulation Patterns ◽  
Tropospheric Circulation ◽  
Phase Variability ◽  
Jet Structure

Abstract The relationship between the October (spring) total ozone column (TOC) midlatitude zonal asymmetry over the Southern Hemisphere (SH) and the stratospheric quasi-stationary wave 1 (QSW1) interannual phase variability is analyzed. Once contributions to the TOC from known global predictors, estimated with a multiregression model, are removed, the residual TOC interannual variability is observed to be dynamically coupled to the stratospheric QSW1 phase behavior. The stratospheric QSW1 interannual phase variability, when classified according to specifically designed indices, yields different circulation patterns in the troposphere and stratosphere. High (upper quartile) index values correspond to a westward rotation of the midlatitude ozone trough and the stratospheric QSW1 phase, while low (lower quartile) index values represent their eastward-rotated state. These values can be associated with statistically different tropospheric circulation patterns: a predominantly single poleward tropospheric jet structure for high index values and a predominantly double-jet structure for low index values. For the latter, there is a higher daily probability of double-jet occurrence in the troposphere and a stronger stratospheric jet. These jet structures and their daily behavior are supported by significant synoptic-scale activity anomalies over SH mid- to high latitudes as well as changes in tropospheric quasi-stationary waves 1–3. The wave activity flux (W flux) diagnosis shows the contribution of active quasi-stationary waves in the observed tropospheric anomalies associated with high and low index values. With low index values, the quasi-stationary waves lead to a self-sustaining state of the stratospheric–tropospheric coupled system. With high index values, the overall mid- to high latitude circulation is associated with wave energy propagation from the tropical central Pacific into higher latitudes. Thus, during the austral spring, there are interactions between the troposphere and stratosphere, leading to the locally well-defined upward and downward propagation of wave anomalies, that is, significant upper troposphere (UT)–lower stratosphere (LS) interactions can occur within a spring month itself.

scholarly journals Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data

2012 ◽  
Vol 30 (10) ◽  
pp. 1463-1477 ◽  
Author(s):  
R. Wang ◽  
S. D. Zhang ◽  
H. G. Yang ◽  
K. M. Huang
Keyword(s):  
Standing Wave ◽  
Zonal Wind ◽  
Lower Stratosphere ◽  
Radiosonde Data ◽  
Wind Component ◽  
Jet Stream ◽  
Fort Worth ◽  
Vertical Wavelength ◽  
Subtropical Jet Stream ◽  
Subtropical Jet

Abstract. The activities of mid-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W) and one Chinese station (Wuhan, 30.5° N, 114.4° E). Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same quasi 16-day wave at the three American stations (Miramar Nas, Santa Teresa and Fort Worth), which propagates steadily along the latitude. The quasi 16-day wave in the stratosphere is also a standing wave with vertical wavelength larger than 10 km in the zonal wind component, and it is westward with the zonal number 1–2. However, the quasi 16-day wave in the stratosphere may not come from the troposphere because of the different concurrent times, propagation directions and velocities. By using the global dataset of NCEP/NCAR reanalysis data, the zonal propagation parameters of 16-day waves in the troposphere and stratosphere are calculated. It is found that the tropospheric 16-day wave propagates eastward with the zonal number 6, while the stratospheric 16-day wave propagates westward with the zonal number 2, which matches well with the results of radiosonde data.

scholarly journals The Effect of Explicit Convection on Couplings between Rainfall, Humidity, and Ascent over Africa under Climate Change

2020 ◽  
Vol 33 (19) ◽  
pp. 8315-8337 ◽  
Author(s):  
Lawrence S. Jackson ◽  
Declan L. Finney ◽  
Elizabeth J. Kendon ◽  
John H. Marsham ◽  
Douglas J. Parker ◽  
...  
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Climate Models ◽  
Regional Climate ◽  
Hadley Circulation ◽  
Moist Convection ◽  
Rain Belt ◽  
Adaptation To Climate Change ◽  
Convective Scale ◽  
Mean Climate

AbstractThe Hadley circulation and tropical rain belt are dominant features of African climate. Moist convection provides ascent within the rain belt, but must be parameterized in climate models, limiting predictions. Here, we use a pan-African convection-permitting model (CPM), alongside a parameterized convection model (PCM), to analyze how explicit convection affects the rain belt under climate change. Regarding changes in mean climate, both models project an increase in total column water (TCW), a widespread increase in rainfall, and slowdown of subtropical descent. Regional climate changes are similar for annual mean rainfall but regional changes of ascent typically strengthen less or weaken more in the CPM. Over a land-only meridional transect of the rain belt, the CPM mean rainfall increases less than in the PCM (5% vs 14%) but mean vertical velocity at 500 hPa weakens more (17% vs 10%). These changes mask more fundamental changes in underlying distributions. The decrease in 3-hourly rain frequency and shift from lighter to heavier rainfall are more pronounced in the CPM and accompanied by a shift from weak to strong updrafts with the enhancement of heavy rainfall largely due to these dynamic changes. The CPM has stronger coupling between intense rainfall and higher TCW. This yields a greater increase in rainfall contribution from events with greater TCW, with more rainfall for a given large-scale ascent, and so favors slowing of that ascent. These findings highlight connections between the convective-scale and larger-scale flows and emphasize that limitations of parameterized convection have major implications for planning adaptation to climate change.

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