Tropical Temperature Research Articles

Spatial and Seasonal Variations of Sea Surface Temperature Threshold for Tropical Convection

Abstract Tropical rainfall variations are of direct societal relevance and drive climate variations worldwide via teleconnections. The convective rainfall tends to occur when sea surface temperature (SST) exceeds a threshold, SSTthr, usually taken to be constant in time and space. We analyze 40-yr monthly observations and find that SSTthr varies by up to 4°C in space and with season. Based on local convective instability, we develop a quantitative theory that largely explains the SSTthr variations using the climatological state of the tropical atmosphere. Although it is often assumed that spatial variations of tropical upper-tropospheric temperature are small and can be neglected, it is shown that lower climatological values favor a lower SSTthr. Similarly, a small increase in climatological surface relative humidity also leads to a decrease in SSTthr, as does a lower climatological air–sea temperature difference. Consequently, efforts to understand and predict natural or forced variations in tropical rainfall must account for, in addition to SST, the temperatures aloft and the near-surface humidity and temperature and requires improved understanding of what controls their distribution in space and time.

Evaluation of NASA POWER and ERA5-Land for estimating tropical precipitation and temperature extremes

Long-term gridded climate data, NASA Prediction of Worldwide Energy Resources (NASA POWER) and the fifth generation of European ReAnalysis Land Component (ERA5-Land), are important alternatives to gauges, but their effectiveness in capturing tropical precipitation and temperature extremes has not been thoroughly studied. Therefore, this study aims to evaluate the performance of NASA POWER and ERA5-Land over the Kelantan River Basin from 1981 to 2020 with 19 gauges in the aspects of climatology characteristics, overall assessment, precipitation detection capability, probability distribution function (PDF), extreme indices calculation, and the 2014–2015 flood. The important findings are as follows: (1) NASA POWER and ERA5-Land are able to reasonably capture the climatology patterns of precipitation, maximum, and minimum temperatures, with the latter performing slightly better; (2) Both products have a better correlation with gauges over coastal regions than inland mountainous regions, but they tend to underestimate precipitation and maximum temperature and overestimate minimum temperature; (3) With high POD values and moderate FAR and CSI values, they are able to detect precipitation days more effectively than non-precipitation days; (4) The PDF assessment reveals that both products overestimate moderate precipitation (1–20 mm/day) and underestimate no/tiny (0–1 mm/day), heavy (20–50 mm/day), and violent (greater than50 mm/day) precipitation; (5) With the exception of CWD and R10mm, both products tend to significantly underestimate most of the precipitation extreme indices, while a better correlation with gauges can be found in the calculations of CDD, R10mm, R20mm, TXx, and TNn; (6) Both products have a higher correlation and a better precipitation detection ability during the 2014–2015 flood, but they significantly underestimate the amount of precipitation. The findings show that NASA POWER and ERA5-Land offer valuable climate information for locations without gauges, but it is recommended to apply bias correction prior to applying them in this tropical basin.

A simple dynamic equilibrium model shows that high phosphatase activity in tropical forest soils could be explained by rapid microbial turnover

Microorganisms and plant roots secrete phosphatase to obtain phosphorus (P) by degrading organic P. Previous studies have reported high phosphatase activity in tropical forest soils, which has been attributed to poor soil P conditions. However, rapid microbial turnover in tropical forest soils can also contribute to the high soil phosphatase activity. To test this, a simplified dynamic equilibrium model was developed. This model was intentionally designed to exclude the pathways of P originating from rock weathering or P adsorption by soils, with the aim of assessing the specific effect of accelerated microbial turnover on soil phosphatase activity. This model showed that accelerated microbial turnover consistently leads to elevated phosphatase activity, irrespective of the parameters, under the assumed environmental condition with the same litter P input. This suggests that rapid soil microbial turnover may serve as another crucial factor contributing to the high phosphatase activity in tropical forest soils, where both moisture and temperature are high.

Naked neck gene and intermittent thermal manipulations during embryogenesis improve posthatch performance and thermotolerance in slow-growing chickens under tropical climates

Many studies have shown that thermal manipulations during the incubation (TMI) and naked neck gene (Na) positively affect heat-stressed broilers' thermotolerance, hatching process, and posthatch performance. Their combination could increase the beneficial effect on broilers reared under natural tropical climatic conditions. The aim of this study was to investigate the effects of the Na gene and TMI on hatching and posthatch performance of slow-growing broilers under tropical climates. The study included 1,200 hatching eggs from 2 different crosses: 1) females and males, both with a normal or fully feathered neck (na na group), and 2) females (with a normal neck) and males (bare neck) (Na na group), incubated in similar conditions until d 7. Thereafter, they were assigned to 3 subgroups for each cross: the control group (C) was incubated at standard incubation conditions (37.8°C, 60% RH). The TMI-1 group was subjected to TMI-1 (T=38.5°C, RH=65%, E10-18, 6 h/d) and TMI-2 group to TMI-2 (T=39.5°C, RH=65%, E7-16, 12 h/d). Between 450 and 504 h of incubation, eggs were checked for hatching events. During the posthatch phase, chicks from each incubation subgroups (Na na-C, Na na-TMI-1, Na na-TMI-2, na na-C, na na-TMI-1, na na-TMI-2) were raised for 12 wk at a tropical natural ambient temperature. Hatchability, hatching time, chick's temperature, final body weight (FBW), and feed conversion ratio (FCR) were determined. The results revealed that the Na gene reduced (P ˂ 0.05) hatchability. The control group had the highest mortality rate compared to TMI-1 and TMI-2 groups. There was an interaction between genotype and TMI on incubation duration, hatching weight, chick quality, FBW, and FCR (P ˂ 0.05). In conclusion, the Na gene influenced the effects of thermal manipulation. TMI-1 combined with Na gene improved the productive performances of broilers in a tropical climate.

A multi-isotopic study reveals the palaeoecology of a sebecid from the Paleocene of Bolivia

Sebecids constitute a family of notosuchian crocodylomorphs of probable terrestrial habits. They are notable for having survived the Cretaceous-Paleogene mass extinction and are known until the Miocene in South America. However, ecological traits that favoured their resilience in continental ecosystems remain unknown. Here, using a multi-isotopic approach, we infer several palaeoecological traits of a sebecid from the locality of Tiupampa (Bolivia), which contains a diverse vertebrate fauna of the Early Paleocene. After having constrained the effects of diagenesis, the study of the oxygen isotope compositions of apatite phosphate allows the identification of water resources for the various studied taxa and to infer an ectothermic thermoregulation strategy for the sebecids. A terrestrial lifestyle is also supported by different oxygen isotope compositions observed between sebecids and aquatic dyrosaurid crocodylomorphs. The radiogenic strontium isotope compositions confirm the continental affinities of this fauna, with no marine input in the palaeoenvironment frequented by the different faunal elements. The calcium and carbon isotope compositions show that the sebecids from Tiupampa were at the top of a C3-based food web. Finally, a local dry environment with tropical temperatures for those specimens is inferred both from oxygen and carbon isotope compositions of their hard tissues.

Can Tibetan Plateau Snow Depth Influence the Interannual Association between Tropical Indian Ocean Sea Surface Temperatures and Rapidly Intensifying Typhoons?

Abstract This study finds that the observed decrease in winter–spring Tibetan Plateau snow depth since 2000 has played an important role in weakening the correlation between rapidly intensifying tropical cyclones over the western North Pacific and tropical Indian Ocean sea surface temperatures (SSTs). Tibetan Plateau snow depth modulates convective activity through changes in the South Asian high. Increased Tibetan Plateau snow depth promotes basinwide tropical Indian Ocean cooling in spring through a Gill-type response. In the following seasons, downward latent heat flux anomalies associated with a weaker monsoon circulation contributes to warm SST anomalies over the western tropical Indian Ocean, thus favoring a positive phase of the Indian Ocean dipole. This evolution of tropical Indian Ocean SSTs associated with anomalously high Tibetan Plateau snow depth potentially weakens the relationship between rapidly intensifying tropical cyclone frequency and spring tropical Indian Ocean SSTs. When the effect of Tibetan Plateau snow depth is removed via partial correlation analysis, we find a significant relationship between spring tropical Indian Ocean SSTs and rapidly intensifying tropical cyclones as well as corresponding large-scale environmental factors. The results of this study enhance understanding of changes in tropical cyclone intensity and have implications for seasonal forecasting of tropical cyclone intensity over the western North Pacific basin. This study also emphasizes the importance of Tibetan Plateau thermal forcing in atmosphere–ocean coupling.

Significant West Antarctic Cooling in the Past Two Decades Driven by Tropical Pacific Forcing

Abstract During the second half of the twentieth century, the West Antarctic Ice Sheet (WAIS) has undergone significant warming at more than twice the global mean and thus is regarded as one of the most rapidly warming regions on Earth. However, a reversal of this trend was observed in the 1990s, resulting in regional cooling. In particular, during 1999–2018, the observed annual average surface air temperature had decreased at a statistically significant rate, with the strongest cooling in austral spring. The spring cooling correlates significantly with the second leading modes (EOF2) derived from empirical orthogonal function (EOF) analysis on the sea level pressure over Antarctica during 1999–2018, associated with the negative phase of the interdecadal Pacific oscillation with an average of cooling of central and eastern tropical Pacific surface sea temperature (SST) anomalies. The EOF2 results in the enhanced cold southerly winds on the continental WAIS through the cyclonic conditions over the Amundsen Sea region and a blocking high in the Drake Passage and northern Antarctic Peninsula, causing the WAIS cooling trend.

Stoichiometry composition of nanofiller SiO2 and ATH to improve properties of silicone elastomer for outdoor high voltage insulators

Silicone elastomer (SE) has several advantages as an insulator material, light weight, dielectric, water repellent (hydrophobic), resistivity, thermal, mechanical and earthquake resistant properties compared to porcelain/ceramic and glass. However, the installation of outdoor insulators with tropical climate temperature exposure above 15 °C, high humidity and uv intensity during the day can degrade its properties which will shorten the life of the insulator. Studies towards improvements to improve the performance of SE insulators under certain conditions can be carried out by using the vulcanization method, formulating the stoichiometry of the filler material. The high-dose filler in SE will increase its mechanical strength and thermal stability, but it can reduce its dielectric properties and the molding process more difficult. Therefore, the purpose of this study was to determine the stoichiometric composition of SiO2 nanofillers and alumina trihydrate (ATH) nanofiller on SE to improve their properties as outdoor high-voltage insulators. Making test-material from silicone rubber resin RTV683 with a mixture of silica powder (20 nm) and ATH powder (20–30 nm). The stoichiometric ratio of resin, filler and hardener compositions varied (80–95: 5–20: 3–7.5). To determine its performance, the specimens were aged by immersing them in 25–50 °C water, artificially polluting and uv radiation the surface to simulate the influence of water diffusion and transfer hydrophobicity to pollution on the surface material. Measurement results before and after treatment indicated that the combination of SiO2 + ATH nanofiller with a composition of 10–15%wt improved the properties of ES such as hydrophobic (average contact angle of water drops > 90°), water absorption < 1.6%, relative permittivity εr < 5, mechanical properties (tensile strength) is 9.57–27.48 N/mm2, surface roughness 0.022–0.153 μm, breakdown voltage 14.8–19.3 kV/cm varies depending on stoichiometric nanofiller, mixing process, curing temperature (50 °C–90 °C) and curing time 2–24 h.

Impacts of seasonal variations of the Tropical Pacific ocean temperatures on upper ocean oxygen response

The El Niño–Southern Oscillation (ENSO) is the most dominant natural variability in the Earth system, which represents seasonal-to-interannual variations of the surface equatorial Pacific Ocean temperatures and subsurface ocean interior. Impacting the physical upper ocean characteristics, ENSO exerts significant influences on the marine ecosystem, such as oxygen and phytoplankton concentrations via strong quasiperiodic oscillation between El Niño (warm phase) and La Niña (cold phase) events. The present study uses observational reanalysis and satellite data to investigate seasonal variations of ENSO and their impacts on marine biogeochemical processes. The results show that the oxygen and chlorophyll anomalies in the upper ocean exhibit different seasonal responses to ENSO. While both the summer and winter season biological responses significantly lag ENSO, the concentration of oxygen and phytoplankton during summer (winter) has no (large) concurrent covariability with ENSO. Given a strong negative correlation between chlorophyll-based indices and El Niño events, increasing mean ocean temperatures and ocean extreme events may induce lower upper-ocean oxygen levels, leading to possible risks in the ecosystem over the tropical Pacific Ocean.

Connection between the Tropical Pacific and Indian Ocean and Temperature Anomaly across West Antarctic

West Antarctic and the Antarctic Peninsula have experienced dramatic warming in austral spring since the 1970s. Using observations and the Community Atmosphere Model version 4 (CAM4), this study explores the physical mechanism by which the tropical Pacific and Indian Ocean temperature anomaly mode (PIM) affects the dipolar surface air temperature (SAT) anomalies across the West Antarctic in austral spring. The positive phase of the PIM, characterized by positive sea surface temperature anomalies (SSTAs) in the tropical central-eastern Pacific and western Indian Ocean and negative SSTAs in the Maritime Continent, can generate two branches of stationary Rossby wave trains propagating from the tropical central Pacific and southeastern Indian Ocean to the West Antarctic, with an anticyclonic anomaly appearing over the Amundsen Sea. The northerlies advect warmer air to the Ross–Amundsen Seas, but southerlies advect colder air to the Antarctic Peninsula–Weddell Sea, resulting in the dipole of SAT anomalies over the West Antarctic. In this process, the role of tropical central-eastern Pacific SSTAs dominate, and it is amplified by the SSTAs around the Maritime Continent. The SSTAs in the western Indian Ocean combined with the SSTAs over the Maritime Continent further contribute to the western pole of the SAT. Only simulation that includes a prescribed PIM forcing can exactly reproduce the observations of the dipolar SAT response across the West Antarctic, indicating the need to treat the tropical Pacific and Indian Oceans as a unified whole.

Tropical Surface Temperature and Atmospheric Latent Heating: A Whole-Tropics Perspective Based on TRMM and ERA5 Datasets

Tropical surface temperature (TST) and its connection with atmospheric heating, including tropical latent heating (TLH), is essential to the interannual variability of tropical atmospheric circulation and global teleconnection. Utilizing seasonally averaged satellite-based TRMM precipitation data as a proxy of TLH and ERA5-based TST data from 1998 to 2018, we reveal some new features in terms of cross-hemispheric connection in the TLH and TST variability by decomposing them into equatorially symmetric and antisymmetric components. We find surprisingly that the spatial patterns of TLH projected upon the first principal components (PC1) of symmetric and antisymmetric TSTs over the whole-tropics, are very similar to each other, seemingly at odds with the classic Mastuno–Gill theory. The similarity in the projected TLH patterns is mainly because the PC1s of symmetric and antisymmetric TSTs co-vary temporally with a very high correlation. We use the spatial pattern of local correlation between symmetric and antisymmetric components, for both TST and TLH to depict geographic dependence of the symmetric–antisymmetric connection. We suggest that a whole-tropics perspective, which takes the different but connected nature of equatorially symmetric and antisymmetric modes across the whole-tropics into consideration, may well be useful in understanding and predicting tropical climate variability because clarifying the puzzle raised in this research from such a perspective about the consistency between the observation and the classic Mastuno–Gill theory is directly related to the fundamental dynamics of tropical systems, such as Walker circulation, monsoons, and their relationship with underlying land and sea conditions.

The response of Tampa Bay to a legacy mining nutrient release in the year following the event

IntroductionCultural eutrophication threatens numerous ecological and economical resources of Florida’s coastal ecosystems, such as beaches, mangroves, and seagrasses. In April 2021, an infrastructure failure at the retired Piney Point phosphorus mining retention reservoir garnered national attention, as 814 million liters of nutrient rich water were released into Tampa Bay, Florida over 10 days. The release of nitrogen and phosphorus-rich water into Tampa Bay – a region that had been known as a restoration success story since the 1990s – has highlighted the potential for unexpected challenges for coastal nutrient management.MethodsFor a year after the release, we sampled bi-weekly at four sites to monitor changes in nutrients, stable isotopes, and phytoplankton communities, complemented with continuous monitoring by multiparameter sondes. Our data complement the synthesis efforts of regional partners, the Tampa Bay and Sarasota Bay Estuary Programs, to better understand the effects of anthropogenic nutrients on estuarine health.ResultsPhytoplankton community structure indicated an initial diatom bloom that dissipated by the end of April 2021. In the summer, the bay was dominated by Karenia brevis, with conditions improving into the fall. To determine if there was a unique carbon (C) and nitrogen (N) signature of the discharge water, stable isotope values of carbon (δ13C) and nitrogen (δ15N) were analyzed in suspended particulate material (SPM). The δ15N values of the discharge SPM were −17.88‰ ± 0.76, which is exceptionally low and was unique relative to other nutrient sources in the region. In May and early June of 2021, all sites exhibited a decline in the δ15N values of SPM, suggesting that discharged N was incorporated into SPM after the event. The occurrence of very low δ15N values at the reference site, on the Gulf Coast outside of the Bay, indicates that some of the discharge was transported outside of Tampa Bay.DiscussionThis work illustrates the need for comprehensive nutrient management strategies to assess and manage the full range of consequences associated with anthropogenic nutrient inputs into coastal ecosystems. Ongoing and anticipated impacts of climate change – such as increasing tropical storm intensity, temperatures, rainfall, and sea level rise – will exacerbate this need.

The CoralHydro2k database: a global, actively curated compilation of coral δ18O and Sr ∕ Ca proxy records of tropical ocean hydrology and temperature for the Common Era

Abstract. The response of the hydrological cycle to anthropogenic climate change, especially across the tropical oceans, remains poorly understood due to the scarcity of long instrumental temperature and hydrological records. Massive shallow-water corals are ideally suited to reconstructing past oceanic variability as they are widely distributed across the tropics, rapidly deposit calcium carbonate skeletons that continuously record ambient environmental conditions, and can be sampled at monthly to annual resolution. Climate reconstructions based on corals primarily use the stable oxygen isotope composition (δ18O), which acts as a proxy for sea surface temperature (SST), and the oxygen isotope composition of seawater (δ18Osw), a measure of hydrological variability. Increasingly, coral δ18O time series are paired with time series of strontium-to-calcium ratios (Sr/Ca), a proxy for SST, from the same coral to quantify temperature and δ18Osw variability through time. To increase the utility of such reconstructions, we present the CoralHydro2k database, a compilation of published, peer-reviewed coral Sr/Ca and δ18O records from the Common Era (CE). The database contains 54 paired Sr/Ca–δ18O records and 125 unpaired Sr/Ca or δ18O records, with 88 % of these records providing data coverage from 1800 CE to the present. A quality-controlled set of metadata with standardized vocabulary and units accompanies each record, informing the use of the database. The CoralHydro2k database tracks large-scale temperature and hydrological variability. As such, it is well-suited for investigations of past climate variability, comparisons with climate model simulations including isotope-enabled models, and application in paleodata-assimilation projects. The CoralHydro2k database is available in Linked Paleo Data (LiPD) format with serializations in MATLAB, R, and Python and can be downloaded from the NOAA National Center for Environmental Information's Paleoclimate Data Archive at https://doi.org/10.25921/yp94-v135 (Walter et al., 2022).

Comparison of ozonesonde measurements in the upper troposphere and lower Stratosphere in Northern India with reanalysis and chemistry-climate-model data

The variability and trend of ozone (O3) in the Upper troposphere and Lower Stratosphere (UTLS) over the Asian region needs to be accurately quantified. Ozone in the UTLS radiatively heats this region and cools the upper parts of the stratosphere. This results in an impact on relative humidity, static stability in the UTLS region and tropical tropopause temperature. A major challenge for understanding ozone chemistry in the UTLS is sparse observations and thus the representation of precursor gases in model emission inventories. Here, we evaluate ozonesonde measurements during August 2016 at Nainital, in the Himalayas, against ozone from multiple reanalyses and the ECHAM6-HAMMOZ model. We find that compared to measurements both reanalyses and ECHAM6-HAMMOZ control simulation overestimate ozone mixing ratios in the troposphere (20 ppb) and in the UTLS (55 ppb). We performed sensitivity simulations using the ECHAM6-HAMMOZ model for a 50% reduction in the emission of (1) NOx and (2) VOCs. The model simulations with NOX reduction agree better with the ozonesonde observations in the lower troposphere and in the UTLS. Thus, neither reanalyses nor ECHAM6-HAMMOZ results can reproduce observed O3 over the South Asian region. For a better representation of O3 in the ECHAM6-HAMMOZ model, NOX emission should be reduced by 50% in the emission inventory. A larger number of observations of ozone and precursor gases over the South Asian region would improve the assessment of ozone chemistry in models.

Superior performance of a trailing edge low-latitude population of an intertidal marine invertebrate

The objective of this study is to compare ecologically relevant measures of performance over a broad range of latitude of a species subjected to climate change. Do populations change in relative function over a wide range of latitude? Are populations at the low latitude trailing edge in danger of extinction in the onset of thermal stress? Coastal marine species with planktonic larvae can range over an enormous span of latitude and thermal environments. The fiddler crab Leptuca pugilator extends from high-latitude (41.75°N) winter-frozen Massachusetts tidal flats in the north to subtropical low latitude flats in Florida (24.55°N), where they may be active at the surface over most of the year. We characterized the air environment for males at three sites (New York – latitude 40.0°N, Beaufort, North Carolina – latitude 34.7°N, Panacea Florida, latitude 30.0°N) over the geographic-thermal range, and found major differences in temperature, wind speed, humidity, and vapor pressure deficit. Florida L. pugilator males preferred warmer sand than North Carolina and New York crabs. Local adaptation to latitude-dependent thermal conditions might suggest tradeoffs in performance as a function of temperature. We examined measures of predator escape performance (running speed and righting speed) and overall condition reflecting endurance rivalry success (endurance on a treadmill and major claw closing force) over a wide range of test temperatures. Predator escape rates increase steadily with increasing temperature, but endurance rivalry measures show an intermediate temperature peak of performance. We tested the hypothesis of tradeoffs, with expected local superiority of performance according to regional thermal differences. But instead, the trailing edge Florida males were superior to the higher latitude populations, over a broad range of temperature, but especially at higher temperatures, for all four types of performance measures. The trailing edge population of L. pugilator, in thermal terms, is therefore likely not vulnerable to near future further effects of warming in terms of performance measures related to male reproductive and feeding activities and escape from predators. Fiddler crabs appear to display niche conservatism for stronger performance at tropical temperatures. Such a natural tropical superiority in performance might have to be accommodated in future conceptions of response of marine species to climate change with broad latitudinal distributions in the tropics.

Thermal Impact of the Southern Tibetan Plateau on the Southeast Asian Summer Monsoon and Modulation by the Tropical Atlantic SST

Abstract While it is commonly accepted that the thermal effect of the Tibetan Plateau (TP) strengthens the Asian summer monsoon, a recent analysis based mainly on idealized model experiments revealed that the TP effect weakened the Southeast Asian summer monsoon (SEASM). Based on both observational analyses and model experiments, the current study further deciphers the physical mechanism for the TP’s thermal impact on the SEASM and the modulation of this impact by the sea surface temperature (SST) in the tropical Atlantic. When diabatic heating is enhanced over the southern TP, the South Asian high (SAH) intensifies and extends eastward, leading to convergence over the southeastern flank of the anomalous upper-level anticyclone and sinking motion that cause downward advection of negative vorticity. Accompanied by this anomalous anticyclonic pattern, the western Pacific subtropical high (WPSH) extends westward and the monsoon over Southeast Asia is weakened. The TP–SEASM relationship is enhanced when SST and convection increase over the tropical Atlantic, which cause an anomalous barotropic wave train propagating southeastward from eastern North America to East Asia, leading to an eastward extension of the SAH and a westward extension of the WPSH. The anomalous heating over the tropical Atlantic also modulates the Walker circulation through two anomalous vertical cells, with ascending motions over the Maritime Continent and the eastern tropical Indian Ocean, inducing a lower-level anticyclone over Southeast Asia as a Gill-type response. Thus, a warming tropical Atlantic can intensify the TP’s thermal forcing, weaken the SEASM, and then modulate the TP–SEASM relationship through both the extratropical wave train and the tropical zonal circulation. Significance Statement The Southeast Asian summer monsoon (SEASM) exhibits significant interannual variability. This study is aimed at better understanding the thermal impact of the Tibetan Plateau (TP) on the interannual variability of SEASM intensity and the possible modulating effect of the tropical Atlantic on the TP–SEASM relationship. We find that enhanced heating over the southern TP weakens the SEASM circulation and its associated precipitation by extending the South Asian high eastward and expanding the western Pacific subtropical high westward. Tropical Atlantic warming enhances this TP–SEASM relationship through both the extratropical wave train and the tropical zonal circulation. Thus, seasonal prediction of the SEASM can be improved by further considering the synergistic impact of the TP’s thermal forcing and the tropical Atlantic surface temperature.

New developmental data of Chrysomya megacephala (Diptera: Calliphoridae) in tropical temperatures and its implications in forensic entomology.

The estimation of the postmortem interval (PMI) is an essential information in death investigations. It is necessary to know the developmental data of the most important necrophagous insect species in every geographical area. Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) is one of the most common species associated with human body decomposition, especially in the tropics, so a precise knowledge of its life cycle is crucial. However, despite its ubiquity, developmental data in a range of tropical temperatures is scarce. For this reason, the aim of this study is to provide the developmental data of the blowfly, C. megacephala, in a range of tropical temperatures and to apply these data in forensic entomology. Four temperatures were examined (i.e., 27.0°C 29.5°C, 32.0°C and 34.5°C) and the time of developments from egg to adult were recorded. To build the growth curves, five larvae per day were measured with a digital caliper. Accumulated degree-days were calculated and the isomorphen diagram for this species was plotted. As we predicted, the results showed that the life cycle of this species was affected by the increasing temperature. The implications of these new data for determining the minimum PMI in forensic entomology were discussed.

Tropical Tropopause Layer Cloud Properties from Spaceborne Active Observations

A significant part of clouds in the tropics appears over the tropopause due to intense convections and in situ condensation activity. These tropical tropopause layer (TTL) clouds not only play an important role in the radiation budget over the tropics, but also in water vapor and other chemical material transport from the troposphere to the stratosphere. This study quantifies and analyzes the properties of TTL clouds based on spaceborne active observations, which provide one of the most reliable sources of information on cloud vertical distributions. We use four years (2007–2010) of observations from the joint Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and CloudSat and consider all cloudy pixels with top height above the tropopause as TTL clouds. The occurrence frequency of TTL clouds during the nighttime is found to be almost 13% and can reach ~50–60% in areas with frequent convections. The annual averages of tropical tropopause height, tropopause temperature, and cloud top height are 16.2 km, −80.7 °C, and 16.6 km, respectively, and the average cloud top exceeds tropopause by approximately 500 m. More importantly, the presence of TTL clouds causes tropopause temperature to be ~3–4 °C colder than in the all-sky condition. It also lifts the tropopause heights ~160 m during the nighttime and lowers the heights ~84 m during the daytime. From a cloud type aspect, ~91% and ~4% of the TTL clouds are high clouds and altostratus, and only ~5% of them are associated with convections (i.e., nimbostratus and deep convective clouds). Approximately 30% of the TTL clouds are single-layer clouds, and multi-layer clouds are dominated by those with 2–3 separated layers.

Recent decrease of the impact of tropical temperature on the carbon cycle linked to increased precipitation

The atmospheric CO2 growth rate (CGR) variability is largely controlled by tropical temperature fluctuations. The sensitivity of CGR to tropical temperature left({{{{rm{gamma }}}}}_{{{{rm{CGR}}}}}^{{{{rm{T}}}}}right) has strongly increased since 1960, but here we show that this trend has ceased. Here, we use the long-term CO2 records from Mauna Loa and the South Pole to compute CGR, and show that {{{{rm{gamma }}}}}_{{{{rm{CGR}}}}}^{{{{rm{T}}}}} increased by 200% from 1960–1979 to 1979–2000 but then decreased by 117% from 1980–2001 to 2001–2020, almost returning back to the level of the 1960s. Variations in {{{{rm{gamma }}}}}_{{{{rm{CGR}}}}}^{{{{rm{T}}}}} are significantly correlated with changes in precipitation at a bi-decadal scale. These findings are further corroborated by results from a dynamic vegetation model, collectively suggesting that increases in precipitation control the decreased {{{{rm{gamma }}}}}_{{{{rm{CGR}}}}}^{{{{rm{T}}}}} during recent decades. Our results indicate that wetter conditions have led to a decoupling of the impact of the tropical temperature variation on the carbon cycle.

Seasonality of the Migrating Semidiurnal Tide in the Tropical Upper Mesosphere and Lower Thermosphere and Its Thermodynamic and Momentum Budget

AbstractThis work uses the Specified Dynamics‐Whole Atmosphere Community Climate Model with Ionosphere/Thermosphere eXtension (SD‐WACCM‐X) to determine and explain the seasonality of the migrating semidiurnal tide (SW2) components of tropical upper mesosphere and lower thermosphere (UMLT) temperature, zonal wind, and meridional wind. This work also quantifies aliasing due to SW2 in satellite‐based tidal estimates. Results show that during equinox seasons, the vertical profiles of tropical UMLT temperature SW2 and zonal‐wind SW2’s amplitudes have a double‐peak structure while they, along with meridional‐wind SW2, have a single‐peak structure in their amplitudes in June solstice. Hough mode reconstruction reveals that a linear combination of five SW2 Hough modes cannot fully reproduce these features. Tendency analysis reveals that for temperature, the adiabatic term, nonlinear advection term, and linear advection term are important. For the winds, the classical terms, nonlinear advection term, linear advection term, and gravity wave drag are important. Results of our alias analysis then indicate that SW2 can induce an ∼60% alias in zonal‐mean and DW1 components calculated from sampling like that of the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics satellite and the Aura satellite. This work concludes that in situ generation by wave–wave interaction and/or by gravity waves plays significant roles in the seasonality of tropical UMLT temperature SW2, zonal‐wind SW2, and meridional‐wind SW2. The alias analysis further adds that one cannot simply assume that SW2 in the tropical UMLT is negligible.