Tropical Air Research Articles

New Insights into Weather and Stroke: Influences of Specific Air Masses and Temperature Changes on Stroke Incidence

Background/Objectives: Meteorological factors seem to influence stroke incidence, however, the complex association between weather and stroke remains unclear. Possible explanations from the literature do not categorize into subdivisions of ischemic strokes, only have small patient numbers, or refer to a selection of isolated weather elements without investigating weather changes and more. Method: In this exploratory trial, almost 18,000 stroke cases from a single stroke center in Southern Germany were analyzed from 2006 to 2015 and classified into the main subgroups of strokes and subdivisions of ischemic stroke etiologies applying the Trial of Org 10172 in Acute Stroke Treatment classification. For each stroke event, the air mass classification was determined from a subset of 7 air mass categories. Relative excess morbidities were derived for the 7 different air mass categories, taking into account the day of the event and up to 2 and 5 days preceding the stroke event. Results: Statistically significant findings (α ≤0.1) reveal that dry tropical air masses were associated with a lower/higher risk for hemorrhagic (HEM)/macroangiopathic strokes (MAS), respectively. Dry polar air masses were associated with a higher risk for intracerebral bleedings and lower risk for ischemic stroke subtypes. Moist air masses were associated with a reduced incidence of MAS. A strong temperature increase 5 days prior to the event was associated with a lower risk of HEM strokes. Temperature increases were associated with lower risks for MAS and cardio-embolic strokes. Significant temperature decreases were associated with a higher risk of MAS. Conclusions: Temperature effects were dependent on both air masses and temperature changes within 5 days prior to the event and were associated with statistically relevant changes in stroke incidence. Decisive factors such as etiology, age, sex, and risk factors were also taken into account.

Remote effect of a tropical cyclone in the Bay of Bengal on a heavy-rainfall event in subtropical East Asia

Torrential frontal rainfall occurred over Northern Taiwan on June 2, 2017. Prior to this rainfall, tropical cyclone (TC) Mora formed in the Bay of Bengal. This study investigated the triggering effect of TC Mora on the heavy-rainfall system through numerical experiments. The numerical experiments, in which TC Mora was included or excluded in the initial conditions, revealed that TC Mora strengthened the southwesterly winds, which effectively transported tropical warm moist air toward Taiwan, and the cool dry northerly winds to the north of Taiwan. The strengthened southeasterly and northerly winds created a strong frontal system near Taiwan. TC Mora contributed to the heavy frontal rainfall by enhancing tropical–extratropical interaction and vertical coupling in East Asia.

Tropospheric ozone retrieval from thermal infrared nadir satellite measurements: Towards more adaptability of the constraint using a self-adapting regularization

We developed a Self-Adapting Constraint Retrieval Scheme (SACRS) to retrieve ozone profiles from nadir infrared satellite measurements. In this algorithm, the constraint is variable in altitude and adapted automatically for each individual measurement. The algorithm is tested on synthetic observations representing the future IASI-NG satellite observations and considering either ozonesonde measurements or chemistry-transport model ozone simulations to represent the true ozone (pseudo-reality). The ozone retrievals are evaluated mainly for the troposphere with a specific focus on the lower troposphere between the surface and 6 km. Compared to a previous algorithm based on a fixed constraint retrieval scheme (FCRS), the biases, correlation and error estimates are improved with the SACRS. The bias is reduced by 40% and the correlation coefficient increases from 0.72 to 0.80. The SACRS algorithm also leads to an enhanced sensitivity in the lower troposphere with degrees of freedom for signal up to 0.83, increased by 11% compared to the FCRS. The SACRS performs especially well where current algorithms usually fail, namely for polar and tropical air masses. The bias is reduced from 8.6% to 0.5% in the troposphere (surface-9 km) when considering polar cases and from 24.4% to 10.1% in the upper troposphere - lower troposphere column (12–18 km) in the tropics.

Role of the East Asian trough on the eastern Mediterranean temperature variability in early spring and the extreme case of 2004 warm spell

This study investigates the potential influence of the East Asian trough (EAT) on the eastern Mediterranean temperature variability in early spring. In connection with this, it also examines the extreme case of the year 2004 when anomalous warming of the eastern Anatolia resulted in unprecedented snowmelt runoff amounts in the Euphrates and Tigris basins in early March. In the analyses, we used reanalysis data, gridded products of surface temperature and snow cover, river discharge data and satellite imagery. We employed an intensity index for the EAT and a trough displacement index for the Mediterranean trough (MedT) to explore the relationship between the strength of the EAT and the displacement of the MedT at pentad resolution. Our analysis shows that there are statistically significant correlations (at 99% confidence level) between the strength of the EAT and the zonal shift of the MedT on some pentads (e.g., 3rd, 13th, 37th and 59th), but that the highest correlation occurs on the 13th pentad of the year corresponding to the early days of March. It seems that, on this pentad, when the EAT is strong, the MedT tends to be located in the west of its climatological position (about $$30\hbox {$-$}35^{\circ }\hbox {E}$$ ) which causes warmer conditions over the eastern Mediterranean. In 2004, which appears to be an extreme year for this phenomenon, the MedT is positioned and deepened in the central Mediterranean (about $$10\hbox {$-$}15^{\circ }\hbox {E}$$ ), and extended towards central Africa during the early days of March. This synoptic pattern provided favorable conditions for the development of a tropical plume/atmospheric river with a southwest-northeast orientation, carrying warm tropical African air towards the eastern Mediterranean and Anatolian highlands resulting in rapid melting of the snowpack as well as severe precipitation, and thus flooding events, in the eastern Anatolia. A key finding in our analysis is that the strengthening of the EAT was instrumental to the increased amplitude of the ridge-trough system over the Euro-Mediterranean region in the early days of 2004 spring. We highlight that the response of surface and upper level meteorological conditions to the amplitude of the ridge-trough system enhanced by the strength of the EAT might be crucial in the understanding of some of the extreme hydrometeorological events in the eastern Mediterranean region.

Wind–Mixed Layer–SST Feedbacks in a Tropical Air–Sea Coupled System: Application to the Atlantic

Abstract The ocean–atmosphere feedback associated with the thermodynamic coupling among wind speed, evaporation, and sea surface temperature (SST), called the wind–evaporation–SST (WES) feedback, contributes to the cross-equatorial SST gradient over the tropical oceans. By conducting an eigenanalyses of simple linear air–sea coupled models, it is shown that two additional feedback processes are present when the variable oceanic mixed layer depth (MLD) is considered. The horizontal structures of the leading modes are similar to the WES mode, which shows a meridional dipole in the SST anomalies straddling the equator with cross-equatorial wind anomalies that represent the weakening/strengthening of the trade winds over the warm/cool SST anomalies. The coupling of the variable MLD with winds and SST more than doubles the growth rate of the WES mode and enhances the equatorward propagation of the coupled disturbances. The identified feedbacks operate as follows: The weaker winds associated with warm SST anomalies shoal the mixed layer through suppressed turbulent mixing, which causes the mixed layer to be more sensitive to the climatological shortwave radiation and amplifies the initial positive SST anomalies. Likewise, deepening of the mixed layer due to stronger winds acts to maintain the negative SST anomaly on the other side of the dipole. The MLD anomalies can also be generated by the buoyancy flux anomaly related to the wind-induced latent heat flux anomaly. The antiphase relationship between the SST and MLD anomalies seen in the simple model bears some resemblance to that which is observed in the observations and a state-of-the-art coupled model during the Atlantic meridional mode.

An Unusual Extreme Rainfall Event in Canberra Australia on February 2018

AbstractA case of an extreme rainfall event in Canberra, the capital city of Australia, on 24–25 February 2018 is investigated. Canberra received more than the long‐term statistical February total rainfall within 6 hr on that day, causing overwhelming flash flooding in the city. In contrast to many coastal cities or tropical regions, Canberra is located at the boundary between the tropics and extratropics and is usually dry and warm in February. The diagnostic analysis shows that this relatively rare brief heavy rainfall was the joint effects of lower‐level warm, moist conveyor belts, the remnants of tropical cyclone Kelvin, surface cold fronts, and a midlatitude trough at middle to upper levels. The lower‐level northeast and west conveyor belts of water vapor contributed to the accumulation of moisture and created favorable conditional instability over Canberra by transporting tropical moist and warm air from Coral Sea and from the Kelvin remnant to Canberra prior to and during the rainfall period. Enhanced uplift was triggered by the arrival of a cold front in the warm, moist unstable air. The rainfall reached a peak 13.6 mm in 30 min soon after a low‐level frontal updraft coupled with middle‐ to upper‐level dynamical uplift ahead of the midlatitude trough. After the passage of the upper‐level trough, the dry, cold air in the rear of the trough stabilized and dried the atmosphere above Canberra. The rainfall decreased and ended rapidly.

Heat waves in Central Europe and tropospheric anomalies of temperature and geopotential heights

The aim of the article was to provide a detailed analysis of pressure conditions, employing the anomalies of geopotential heights, during the occurrence of heat waves in Central Europe, but also in the days preceding and following their occurrence. The study uses data from 1966 to 2015 from the Institute of Meteorology and Water Management—National Research Institute, Deutscher Wetterdienst and the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR). A heat wave was defined as a sequence of at least 3 days with a maximum daily air temperature of >30°C. The study showed an increase in the number of hot days, which was statistically significant in the majority of the area. In the analysed years, an increasing number of heat waves were recorded, and this occurrence was associated with high pressure systems. Anticyclonic blocking in the summer inhibits the zonal flow of air masses and intensifies meridional flow, which in Central Europe in the summer means the presence of polar continental and tropical air masses. During heat waves, there were positive anomalies of isobaric surface heights over the study area with a maximum in the upper troposphere. On average, anomalies at the 300 hPa pressure level began to form over the Atlantic Ocean. Determining atmospheric preconditions of persisting blocking events in summer resulting in heat waves may be helpful in predicting thereof.

Spring and summer time ozone and solar ultraviolet radiation variations over Cape Point, South Africa

Abstract. The correlation between solar ultraviolet radiation (UV) and atmospheric ozone is well understood. Decreased stratospheric ozone levels which led to increased solar UV radiation levels at the surface have been recorded. These increased levels of solar UV radiation have potential negative impacts on public health. This study was done to determine whether the break-up of the Antarctic ozone hole has an impact on stratospheric columnar ozone (SCO) and resulting ambient solar UV-B radiation levels at Cape Point, South Africa, over 2007–2016. We investigated the correlations between UV index, calculated from ground-based solar UV-B radiation measurements and satellite-retrieved column ozone data. The strongest anti-correlation on clear-sky days was found at solar zenith angle 25∘ with exponential fit R2 values of 0.45 and 0.53 for total ozone column and SCO, respectively. An average radiation amplification factor of 0.59 across all SZAs was calculated for clear-sky days. The MIMOSA-CHIM model showed that the polar vortex had a limited effect on ozone levels. Tropical air masses more frequently affect the study site, and this requires further investigation.

Effects of a multilayer snow scheme on the global teleconnections of the Indian summer monsoon

Eurasian snow is one of the slowly varying boundary forcings known to have significant influences on the mean and variability of the Indian summer monsoon rainfall (ISMR). A multilayer complex snow scheme, incorporated into the state‐of‐the‐art coupled Climate Forecast System version 2 (CFSv2) showed significant improvements in the simulation of mean ISMR, snow, and Northern Hemisphere surface and tropospheric temperature. Here we show that a realistic simulation of high‐latitude snow decreases the north–south temperature gradient, which in turn decreases the meridional transport of energy from the Equator to the Pole, consequently affecting the tropical sea surface temperature (SST) and air–sea interactions. The global teleconnections of the ISMR with SST and 2 m temperature over land are also improved considerably in association with improved simulation of the oceanic natural modes of variability. Our findings provide new insights for the relationship between the winter Eurasian snow and the following ISMR, namely that the same relationship may be understood through a framework of meridional atmospheric energy transport and its effects on the tropical air–sea interactions. The improvements in the global teleconnection in the modified version of CFSv2 may have implications in the ISMR predictability and prediction skill.

Characterization of TSP (Si, Pb and Ca) from tropical ambient air during building construction project

Apartment development in urban areas is often proposed as solution to meet the housing needs. However, building construction could contribute air pollutants that have a negative impact on health. This activity could generate Total Suspended Particulate (TSP). This study aimed to quantify the composition of TSP (Si, Pb and Ca) arising from building construction activities and comparing the measurement results with the air quality standard in Indonesia. The sampling method was undertaken according to SNI 19-7119.3-2005. Based on this research, the TSP concentration in samples has exceeded the permissible limit (the highest concentration of TSP was 786, 13 µg/m3). The result of characterization of TSP indicates that the highest Si concentration was found at the point of transportation path, while Pb and Ca.

Change in the Synoptic Regime of Tomsk in the Late 20th–Early 21st Centuries

Synoptic processes that occurred in the Tomsk region between 1993 and 2016 are analyzed. A significant decrease in the difference between the frequency of cyclones and anticyclones over the past decade is revealed. There are tendencies to a decrease in the frequency of Arctic air mass invasion, and to an increase, of subtropical and tropical air masses.

The influence of tropical and subtropical air masses on the chemical composition of the tropospheric aerosol of Western Siberia based on the results of systematic aircraft sounding in 1997-2017

Almost monthly sensing of the troposphere from 500 to 7000 m above Karakansky bor (Novosibirsk Province) are conducted since 1997 up to now by using of the aircraft-laboratory "Optik" based on Antonov-30 or Tupolev-134. Aerosol sampling on to Petryanov filters AFA-CP-20 for subsequent laboratory quantitative analysis of the content of inorganic ions and the next elements in the aerosol composition: Al, Ba, Ca, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sn, Ti, V, Be, Cd, Si, Co, Cr, Sr, Zn, Zr was performed for each flight. For the region of the study of tropospheric aerosol, the chemical composition of the aerosol was classified for the main air masses during the period of airborne sounding from September 1997 to June 2017 - continental arctic, continental moderate, and combined into one “southern” group of the continental tropical and subtropical air masses. Explicit "southern" origin, along with silicon, have chromium, manganese, silver and bicarbonate-anion. To the same group, the ions of chlorine and sodium are attracted, which probably were transported together with salt particles originating from Central Asian deserts.

Study of Air Composition in Different Air Masses

Data of multiyear monitoring at the TOR station are used to calculate the average concentrations of gas and aerosol constituents in different air masses in the region of Tomsk. It is shown that CO2 and CH4 are characterized by a decrease in concentrations in going from an Arctic to a tropical air mass. Ozone shows the opposite pattern: the largest concentrations are recorded in the tropical air mass and the smallest concentrations in the Arctic air mass. Such gases as CO and SO2 show distributions more complex in character.

Detecting Clouds Associated with Jet Engine Ice Crystal Icing

Over 150 jet engine power-loss and damage events have been attributed to a phenomenon known as Ice Crystal Icing (ICI) during the past two decades. Attributed to ingestion of large numbers of small ice particles into the engine core, typically these events have occurred at high altitudes near large convective systems in tropical air masses. In recent years there have been substantial international efforts by scientists, engineers, aviation regulators and airlines to better understand the relevant meteorological processes, solve critical engineering questions, develop new certification standards, and devise mitigation strategies for the aviation industry. One area of research is the development of nowcasting techniques based on available remote sensing technology and cloud models to identify potential areas of high ice water content (HIWC) and enable the provision of alerts to the aviation industry. An international consortium of researchers has investigated various methods for detecting the HIWC conditions associated with ICI. Multiple techniques have been developed using geostationary and polar orbiting satellite products, numerical weather prediction model fields, and ground based radar data as the basis for HIWC products. Targeted field experiments in tropical regions with high incidence of ICI events have provided data for product validation and refinement of these methods. Beginning in 2015, research teams have assembled at a series of bi-annual workshops to exchange ideas and standardize methods for evaluating performance of HIWC detection products. This paper provides an overview of the approaches used and the current skill for identifying HIWC conditions. Recommendations for future work in this area are also presented.

North Atlantic Summertime Anticyclonic Rossby Wave Breaking: Climatology, Impacts, and Connections to the Pacific Decadal Oscillation

AbstractAnticyclonic Rossby wave breaking (RWB) is characterized by the rapid and irreversible deformation of potential vorticity (PV) contours on isentropic surfaces manifesting as a pair of meridionally elongated high- and low-PV tongues that transport extratropical stratospheric air equatorward and tropical tropospheric air poleward, respectively. Previous studies have noted connections between different types of RWB and the modulation of localized atmospheric phenomena such as the North Atlantic Oscillation (NAO) and tropical cyclogenesis. Despite being the season in which anticyclonic RWB events are most prevalent, no work has focused solely on the frequency, genesis, or variability of the synoptic environment surrounding the equatorward branch of anticyclonic RWB events during the North Atlantic summertime, providing motivation for this study. Using 58 years (1960–2017) of NCEP–NCAR reanalysis data, a comprehensive spatiotemporal climatology of North Atlantic equatorward anticyclonic RWB identified on the 350-K isentropic surface is developed and the synoptic environment surrounding these events from time- and high-PV-tongue centroid-relative perspectives is investigated. Consistent with previous studies, composites suggest that high-PV tongues associated with equatorward anticyclonic RWB introduce anomalously dry, stable extratropical air into the tropical environment, subsequently inhibiting convection there. Additionally, a connection between atmospheric responses to Pacific decadal oscillation (PDO) sea surface temperature (SST) anomalies and the intrabasin frequency of anticyclonic RWB events is uncovered and explored. Results from this study may aid short- to medium-range forecasts of North Atlantic tropical convection, with applications extending into the field of tropical cyclogenesis forecasting.

STUDYING THE MOVEMENT OF THE INTER TROPICAL CONVERGENCE ZONE (ITCZ) OVER AFRICA INVERNAL EQUINOX

In this study, we have tried to study the movement of the Inter Tropical Convergence Zone (ITCZ) over Africa in April by analyzing Temperature, (U, V) Wind and rainfall, studying oscillation of the ITCZ and its relationship with temperature in the different seasons, within the range of Africa in a long period of time (statistical period of 60 years). This is the first long term (monthly, annually, and decadal) study of the ITCZ over Africa, In this study, not only the exact position of ITCZ over Africa is determined but also its position change in the period of 60 years, These results could be used in studying the impacts of ITCZ on climate variations due to changes of position and movement of ITCZ, over Africa also the direct impacts of this movement on sudden changes of seasons start and end of untimely rains. Through the study of the ITCZ movement over Africa in vernal equinox, we find that it is limited between latitudes 2o N to 18o N, and the speed and direction of wind coming from the Tropical Continental air mass (cT) masses in addition to temperature, as well speed and direction of wind coming from the Tropical Maritime air mass (mT) air masses, all of them effect on the movement of ITCZ to the north and south, in different decades, which led to displacement of rain belt over Africa from north to south and vice versa , in addition to change in the amount of Total rainfall over the Abyssinian Plateau during the different decades .

Precipitation Sensitivity to Local Variations in Tropical Sea Surface Temperature

AbstractThe driving of tropical precipitation by the variability of the underlying sea surface temperature (SST) plays a critical role in the atmospheric general circulation. To assess the precipitation sensitivity to SST variability, it is necessary to observe and understand the relationship between precipitation and SST. However, the precipitation–SST relationships from any coupled atmosphere–ocean system can be difficult to interpret given the challenge of disentangling the SST-forced atmospheric response and the atmospheric intrinsic variability. This study demonstrates that the two components can be isolated using uncoupled atmosphere-only simulations, which extract the former when driven by time-varying SSTs and the latter when driven by climatological SSTs. With a simple framework that linearly combines the two types of uncoupled simulations, the coupled precipitation–SST relationships are successfully reproduced. Such a framework can be a useful tool for quantitatively diagnosing tropical air–sea interactions. The precipitation sensitivity to SST variability is investigated with the use of uncoupled simulations with prescribed SST anomalies, where the influence of atmospheric intrinsic variability on SST is deactivated. Through a focus on local precipitation–SST relationships, the precipitation sensitivity to local SST variability is determined to be predominantly controlled by the local background SST. In addition, the strength of the precipitation response increases monotonically with the local background SST, with a very sharp growth at high SSTs. These findings are supported by basic principles of moist static stability, from which a simple formula for precipitation sensitivity to local SST variability is derived.

Synoptyczne uwarunkowania napływu mas powietrza arktycznego i zwrotnikowego nad Lubelszczyznę

<p>Celem opracowania jest charakterystyka częstości i uwarunkowań synoptycznych napływu mas powietrza arktycznego i zwrotnikowego nad obszar Lubelszczyzny. Ich występowanie w ujęciu regionalnym określono dla godziny 12 UTC na podstawie dolnych map synoptycznych PIHM/IMGW z okresu 1951-2010. Do oceny uwarunkowań synoptycznych napływu analizowanych mas powietrza wykorzystano kalendarz typów cyrkulacji dla Lubelszczyzny. Częstość napływu mas powietrza arktycznego w ciągu roku wynosiła 13,4%. Największy udział tych mas występuje wiosną, z maksimum w kwietniu (20,4%), najmniejszy zaś latem (w lipcu i sierpniu poniżej 5%). Rzadziej notuje się napływ powietrza zwrotnikowego (4,1% wszystkich dni w roku). Najczęściej nad Lubelszczyzną występuje ono w lecie (z maksimum w lipcu – 9,2%), natomiast najrzadziej w zimie (< 1%). W latach 1951-2010 zaznaczyły się istotne zmiany w częstości napływu nad Lubelszczyznę mas arktycznych (wzrost średnio o 8 dni na 10 lat) i zwrotnikowych (wzrost o blisko 3 dni na 10 lat). Udział mas arktycznych zwiększył się w zimie, jesieni i na wiosnę, mas zwrotnikowych zaś w lecie. We wszystkich porach roku największe prawdopodobieństwo występowania powietrza arktycznego notowano podczas typów cyrkulacji ze składową północną i północno-wschodnią, najmniejsze zaś w typach warunkujących adwekcję powietrza z południa i południo-zachodu. W przypadku powietrza zwrotnikowego największe prawdopodobieństwo jego wystąpienia notuje się podczas napływu powietrza z kierunków E-SE-S-SW. Niezależnie od pory roku, podczas występowania powietrza arktycznego i zwrotnikowego wykazano występowanie wyraźnych anomalii, zarówno temperatury powietrza na powierzchni izobarycznej 850 hPa, jak i średniej grubości warstwy powietrza między powierzchnią izobaryczną 850 i 1000 hPa.</p>

A Lagrangian Model Diagnosis of Stratospheric Contributions to Tropical Midtropospheric Air

AbstractAirborne in situ observations during the Convective Transport of Active Species in the Tropics campaign in January–February 2014 revealed a large region over the tropical western Pacific where the midtroposphere had a layered structure with a distinct chemical signature of high ozone and low water vapor (HOLW). The observed anticorrelation between ozone and water vapor is a strong indication of transport from the midlatitude upper troposphere and lower stratosphere. This work presents a diagnosis of stratospheric air in the tropical western Pacific midtroposphere through isentropic transport and mixing. Using the Chemical Lagrangian Model of the Stratosphere, we characterize and quantify the contribution of transported stratospheric air to the observed HOLW layers. The result indicates that the isentropic transport is an effective process for stratospheric air to mix into the tropical midtroposphere. Using the modeled stratospheric tracer and 3‐D back trajectories, we identified that 60% of the observed HOLW air masses contain significant stratospheric influence. We have also examined possible contribution to the HOLW layer from ozone production related to biomass burning emissions. Clear chemical signature of this process is found in ∼8% of the HOLW air masses, identified by positive correlations among O3, HCN, and CO. This analysis provides the first quantitative diagnosis of the contribution from the stratosphere‐to‐troposphere transport, highlights the importance of mixing in chemical transport, and demonstrates the limitations of pure Lagrangian trajectory calculations in quantifying transport.

Contribution of Greenhouse Gas Radiative Forcing and Atlantic Multidecadal Oscillation to Surface Air Temperature Trends

The contributions of radiative forcing of greenhouse gases (GHG) and Atlantic Multidecadal Oscillation (AMO) to the trends in global surface air temperature (GST) and surface air temperature for different latitude bands are estimated. Instrumental observational data obtained since the middle of the 19th century and three-component autoregressive models are used. Characteristics of influences of both factors on GST (Wiener–Granger causality) are obtained. The contribution of AMO over the length intervals of 15–30 years appears comparable in absolute value to the contribution of GHG and sometimes even exceeds it, while its contribution over 60-year and longer periods is insignificant. During the recent decades, GHG contribute stronger to the trends of GST and tropical surface air temperature, while their contribution to the trends in surface air temperature in the middle and high latitudes is smaller.