Tropical Temperature Research Articles

Improved complete ensemble empirical mode decompositions with adaptive noise of global, hemispherical and tropical temperature anomalies, 1850–2021

ICEEMDAN, a variant of Empirical Mode Decomposition (EMD), is used to extract temperature cycles with periods from half a year to multiple decades from the HadCRUT5 global temperature anomaly data. The residual indicates an overall warming trend. The analysis is repeated for the Southern and Northern Hemispheres as well as the Tropics, defined as areas lying at or below 30 degrees of latitude. Multiannual cycles explain the apparently anomalous pause in global warming starting around 2000. The previously identified multidecadal cycle is found to be the most energetic and to account for recent global warming acceleration, beginning around 1993. This cycle’s amplitude is found to be more variable than by previous work. Moreover, this variability varies by latitude. Sea ice loss acceleration is proposed as an explanation for global warming acceleration.

Mitigation of Systematic Noise in F16 SSMIS LAS Channels Observations for Tropical Cyclone Applications

The Special Sensor Microwave Imager Sounder (SSMIS) onboard the Defense Meteorological Satellite Program (DMSP) F16, launched on 18 October 2003, was the first conical-scanning radiometer to combine the Special Sensor Microwave/Imagers (SSM/I), Special Sensor Microwave/Temperature Sounder (SSM/T), and the Special Sensor Microwave/Water Vapor Sounder (SSM/T2). Nearly 20 years of F16 SSMIS data are available to the general public, providing many opportunities to study the atmosphere at both the synoptic and decadal scales. However, data noise from complicated structures has occurred in the brightness temperature (TB) observations of lower atmospheric sounding (LAS) channels since 25 April 2013. We used a two-dimensional Fast Fourier Transform to analyze the characteristic features of data noise in cross-track and along-track directions. We found that the data noise is around 1–2 K and occurs at certain cross-track wavelengths (Δλ)noise. A latitudinal variation was found for (Δλ)noise. Due to noise interference, TB observations reflecting rain, clouds, tropical cyclone warm core, temperature, and water vapor distributions are not readily distinguishable, especially in channels above the middle troposphere (channels 4–7 and 24), whose dynamic TB range is smaller than low tropospheric channels 1–3. Examples are provided to show the impact of the proposed noise mitigation for conical-scanning TB observations to capture 3D structures of hurricanes directly. Once the noise in F16 SSMIS LAS channels from 25 April 2013to the present is eliminated, we may investigate the decadal change of many features of tropical cyclones derivable from these TB observations.

Dynamical Seasonal Prediction of the Asian Summer Monsoon in the China Meteorological Administration Climate Prediction System Version 3

Based on the 20 years of ensemble hindcast data, we evaluated the performance of the new version climate prediction system developed by the China Meteorological Administration (CMA CPSv3) on the Asian summer monsoon (ASM) seasonal prediction in this study. Many major features of the ASM are well predicted by CPSv3, including the intensity and location of the heavy precipitation centers, large-scale monsoon circulations, monsoon onset, and the interannual variation of dynamical monsoon indices. The model captures realistically interannual variability of the summer western North Pacific subtropical high (WNPSH) and is highly skillful for the WNPSH index. Compared with its predecessor, the prediction skill of summer precipitation over Asia in CPSv3 is obviously improved, especially over eastern China. The improvement mainly benefits from skillful predictions of the tropical Pacific Ocean and tropical Indian Ocean sea surface temperatures and ocean–atmosphere coupling associated with them.

World Coronavirus Death Regions & Why

Data analysis of the world’s coronavirus deaths and their locations was conducted from April 2020 through November 2021. The Worldometer Coronavirus was used exclusively for this analysis. It was decided to focus on deaths rather than cases as the deaths per case varied widely across the world from as low as 0.5% to as high as 10+%. Although it was expected that there would be variations in accounting from country to country, expectation was also that deaths were definitive. Although the actual death numbers were meaningful, what was far more important was the when, where, and why the deaths occurred in specific locations. The concept of locations initially was considered countries, but was altered to mean regions of the world as this analysis proceeded. What became apparent as this analysis continued was that the deadly coronavirus regions had common attributes of importance. The most important identified include (a) geography and topography, (b) population density and urban population, (c) seasonal meteorology meaning world tropical jet streams and temperature inversions created, (d) major sources of pollution emissions.

Effect of Biopesticide from the Stems of Gossypium Arboreum on Pink Bollworm and Lepidoptera

Pink bollworm and Lepidoptera development quickly in numbers which is a typical animal group that produces around 100 youthful ones inside certain days or weeks. This assault influences the harvests broadly in the tropical and sub-tropical temperature areas. Thus, to keep up with the yield of harvests the vermin ought to be kept away by utilizing pesticides. The unnecessary measure of the purpose of pesticides influences the dirt, land, and as well as human well-being, and contaminates the climate. Thus, an ozone-accommodating biopesticide is extracted from the stems of the Gossypium arboreum. Thus, the extraction of biopesticide from the stems of Gossypium arboreum demonstrated that the quantity of pink bollworm and Lepidoptera is diminished step by step in the wake of showering the arrangement on the impacted region of the plant because of the presence of the gossypol.

Glycerol dialkyl glycerol tetraether signatures in tropical mesotidal estuary sediments of Qua Iboe River, Gulf of Guinea

The continuous supply of land derived organic carbon by rivers is significant to the ocean carbon cycle. In river-estuary systems, the composition and distribution of sedimentary organic matter (OM) can provide detailed information on the balance of land-derived inputs and in situ productivity. This insight is significant for an improved understanding of anthropogenic activity and the changing climate. In the Gulf of Guinea (GoG), high rainfall, coupled with flooding and a warmer climate have direct impacts on OM distributions. Glycerol dialkyl glycerol tetraethers (GDGTs) have been used extensively to investigate OM. In this study, we focused on the widespread occurrence of isoprenoid GDGTs (isoGDGTs), branched GDGTs (brGDGTs), H-tetraethers (H-isoGDGTs and H-brGDGTs), hydroxyl GDGTs (OH-GDGTs), isoGDGT isomers, methylated isoGDGTs (Me-GDGTs), butanetriol and pentanetriol tetraethers (BDGTs and PDGTs), in short sediment cores collected from the inner and outer Qua Iboe River Estuary, located in the GoG. We further determined total organic carbon (Corg), total nitrogen (TN), long chain hydrocarbons (LCA; C27–C33n-alkanes), dinosterol, brassicasterol and phytol, to estimate OM sources, flooding activity, OM degradation, to reconstruct pH and to determine past tropical temperatures. The distribution patterns of GDGTs, use of principal component analysis (PCA), heatmap hierarchical cluster analysis, correlation models, the ratios of isoGDGTs/brGDGTs, ring index (RI), brGDGT-IIIa/IIa, branched and isoprenoid tetraether (BIT), Corg/TN and terrestrial-marine biomarker ratio (TMBR) were all sensitive for indicating terrestrial vs marine OM contributions to the total OM of the tropical estuarine sediments. Marine OM persisted from subsurface to bottom sediment layers (8–38 cm) in the outer estuary site, while a mixed OM source was observed in inner estuary sediments. The Cren/Cren’ ratio >58.5 (up to 83.8), pointed to a predominance of Thaumarchaeota group I.1a microbes. The Methane Index (MI) and isoGDGT-0/Cren ratio indicated significant imprints of a non-methanotrophic archaeal community. A positive linearity of total BDGTs and PDGTs plotted against MI and isoGDGT-0/Cren suggested that these compounds are produced by the same group of the non-methanogenic archaeal community in this tropical estuary. Thus, Methanomassiliicoccus luminyensis is not the only source of BDGTs and PDGTs in the marine environment. Further, the calculated CBT5me derived pH reflected in situ measured sediment pH (6.3). TEX86H-derived sea surface temperature (SST), within error, reflected water column temperature. Calculated brGDGT mean annual air temperatures (MAATs) reflected average annual atmospheric temperatures. Ring index OH-GDGTs temperature proxies (RI-OH SSTsummer and RI-OHꞌ SST) reflected mean dry season (November to February) temperatures. A newly derived MAAT proxy, calculated from H-brGDGT, also reflected the tropical annual air temperature (23–28 °C). Altogether, as expected, the OM sources are traced largely to both terrestrial and marine inputs. The terrestrial OM was deposited by excess flooding and surface runoff occasioned by torrential monsoon rains in recent years, triggered by climate change, while mesotidal currents introduced marine OM into the Qua Iboe River Estuary system. This study further contributes to our understanding of OM distributions in warmer climate conditions.

Effects of Tropical Cyclones on Ozone Pollution in the Pearl River Delta in Autumn

Based on the tropical cyclone track data in the northwest Pacific Ocean from 2015 to 2020, meteorological observation data, and ozone concentration monitoring data in the Pearl River Delta (PRD), the impacts of four tropical cyclones, namely the westbound tropical cyclone (type A), East China Sea tropical cyclone (type B), offshore tropical cyclone (type C), and offshore tropical cyclone (type D), on ozone concentration in the PRD were analyzed. The results showed that:under the influence of the type A tropical cyclone, the risk of regional ozone concentration exceeding the standard exhibited little change. Under the influence of the type B tropical cyclone, the risk of ozone exceeding the standard in the PRD was obviously increased. Under the influence of the type C tropical cyclone, the risk of regional ozone exceeding the standard obviously increased, but the increase was weaker than that of the type B tropical cyclone. The type D tropical cyclone was far away from the Chinese mainland and had little influence on ozone concentration in the PRD. When the type A or type C tropical cyclones occurred, the average daily maximum 8-hour average ozone concentration (MDA8) in the PRD region increased by approximately 5 μg·m-3, and the ozone MDA8 in some cities may have decreased. When the type B tropical cyclone occurred, the regional ozone MDA8 increased by 19 μg·m-3 on average, and the ozone concentration in all cities increased significantly. Among them, the average increase in ozone MDA8 in Zhuhai and Jiangmen was relatively large, with an increase of greater than 20 μg·m-3. Generally speaking, the ozone concentration in cities in the western PRD was more affected by tropical cyclones. When the type B tropical cyclone occurred, solar radiation increased, sunshine duration lengthened, cloud cover decreased, air temperature rose, and relative humidity decreased in the PRD, all of which were beneficial to photochemical reactions. Meanwhile, downward flow increased in the boundary layer, and downward flow transported high-concentration ozone to the ground, which promoted the increase in ozone concentration on the ground. When type A or type C tropical cyclones occurred, the change in meteorological conditions was not entirely conducive to the increase in ozone concentration, and in some cases, even adverse meteorological conditions such as rainfall occurred, which led to the risk of regional ozone exceeding the standard being less than that of the type B tropical cyclone. Affected by tropical cyclones, sunshine hours and air temperature in western cities of the PRD increased more than those in eastern cities, which was more conducive to ozone generation.

Influence of the Amazon‐Orinoco Discharge Interannual Variability on the Western Tropical Atlantic Salinity and Temperature

AbstractOver the last three decades, extreme floods have become increasingly frequent in the Amazon basin, affecting strongly the population and ecosystems of the area. However, the impact of these extreme events on the tropical Atlantic Ocean is still poorly known. In this study, we use a 1/4° coupled ocean‐atmosphere model to assess the impact of the runoff interannual variability on the sea surface salinity and sea surface temperature of the area. Twin sensitivity experiments are performed, forced alternatively with interannually‐varying and climatological river runoff. Composite fields for the highest floods and lowest floods are also compared. This combination of sensitivity tests and composite extremes allows to separate the effect of runoff interannual variability from the rest of the variability (typically driven by mixing, advection and precipitation). We show that the runoff interannual variability modulates the sea surface salinity of the Amazon plume with the same order of magnitude as the salinity variability driven by ocean dynamics and atmospheric forcing. However, due to vertical mixing, this oceanic imprint of the extreme floods is limited to a few months and a few hundred kilometers from the mouth. Years of extreme floods generally coincide with anomalous phases of the Atlantic Meridional Mode, which are associated with large‐scale sea surface temperature anomalies over the tropical Atlantic Ocean. Our results did not reveal any significant modulation of these temperature anomalies by the runoff interannual variability, at any time of the year, questioning the relevance of a hydrological feedback on the tropical Atlantic sea surface temperature.

Soil carbon and microbes in the warming tropics

Abstract Climate warming could destabilise the Earth's largest terrestrial store of reactive carbon (C), by accelerating the decomposition of soil organic matter. A third of that C store resides in the tropics. The potential for tropical soils to sequester C, or to act as an additional source of CO2, will depend on the balance of C inputs and outputs, mediated by the response of soil microbial communities and their activity to perturbation. We review the impact of warming on microbial communities and C storage in humid tropical forest soils over multiple time‐scales. Recent in situ experiments indicate high sensitivity of tropical forest soil C mineralisation to warming in the short term. However, whether this will translate into long‐term soil C decline remains unclear. At decadal time‐scales, high sensitivity of soil C mineralisation to warming is consistent with the correlation between the inter‐annual variation in the tropical land surface temperature and atmospheric CO2 growth rate, and with simulations using the Carnegie‐Ames‐Stanford Approach biosphere model. This observed sensitivity may further contribute to climatic change over millennial time‐scales, suggested by radiocarbon dating of organic matter in river basins showing a twofold acceleration in tropical soil C release during the late‐glacial warming period. However, counter to this evidence, long‐term stability of tropical soil C is suggested by observed steady‐state soil C turnover across temperature gradients with elevation, and by the presence of C in tropical soils that pre‐dates the Holocene Thermal Maximum and late‐glacial warming periods. To help reconcile these recent experimental findings and long‐term observations, we propose mechanisms to explain tropical soil C and microbial responses to warming across multiple time‐scales. Combined in situ experimental and monitoring approaches—large‐scale and cross‐site—are urgently needed to resolve the interplay of these mechanisms across spatial and temporal scales, to shape a better understanding of the relationship between soil microbes and C storage in tropical soils. Read the free Plain Language Summary for this article on the Journal blog.

Reduction of Equatorial Obduction by Atmospheric Intraseasonal Oscillations in the Western and Central Pacific Ocean

AbstractObduction is the large‐scale, irreversible upward water transport from the permanent pycnocline to the surface mixed layer. Using Hybrid Coordinate Ocean Model (HYCOM), this study explores the impact of atmospheric intraseasonal oscillations (ISOs) on the Pacific equatorial obduction that plays a fundamental role in regulating the tropical Pacific climate. Parallel HYCOM experiments forced by atmospheric fields with and without ISO variability are compared to assess the effect of ISOs on the ocean. The results suggest that the ISOs can reduce the annual obduction rate of the western and central equatorial Pacific Ocean (WCEPO; 150°E−160°W, 5°S–5°N) by ∼12%, and their impact on the eastern Pacific is rather limited. The ISOs cause prominent intraseasonal variability of mixed layer depth (MLD) in the WCEPO primarily through surface wind forcing, which in turn affects the two key processes controlling the annual obduction rate. First, the intraseasonal MLD deepening events narrow down the total time windows for obduction by ∼30% and thereby give rise to the decrease in obduction rate; second, it leads to high‐frequency entrainment events and enhances the entrainment rate by ∼18%. The increased entrainment rate is overwhelmed by the reduced time windows for effective entrainment, and the net effect of ISOs is to reduce the obduction rate and modify its seasonal cycle. This work highlights the importance of atmospheric ISOs in the equatorial ocean dynamics, with implications for tropical surface temperature and climate variabilities and biogeochemical cycle.

Mechanisms and kinetics of (de-)protection of soil organic carbon in earthworm casts in a tropical environment

Earthworms have potential to stabilize soil organic carbon (SOC), but the biophysical controls on SOC dynamics in earthworm casts and the SOC residence time in casts is poorly known. To this end, we aimed to investigate (1) the kinetics of SOC (de-) protection in earthworm casts deposited in a tropical environment and (2) changes in the spatial relationships between fresh particulate organic matter (POM) and pore architecture within casts. Our experimental approach was to espose casts produced by the anecic earthworm Amynthas adexilis to tropical temperature and rainfall by placing them in a woodland in northern Vietnam. For 400 d, we monitored the dynamics of cast microstructures using X-ray micro-computed tomography and compared them to those of the surrounding soil aggregates (control). We also measured potential CO2 emissions of the same samples in a laboratory incubation. As expected, recently egested casts had higher SOC (1.9-fold) and POM volumes (7-fold) than aggregates, whereas their total imaged porosity was 4 times less. The SOC of casts was more labile than SOC of aggregates, as casts had 3 times more potentially mineralizable SOC. By 72 d of exposure to field conditions, the casts and aggregates had similar potential SOC mineralization, indicating that they had developed a similar level of SOC protection. Temporal changes in SOC mineralization rates were related to variations in POM volume, particularly those connected to the outside of the cast. After 400 d of exposure, casts had still greater POM volumes (2.5-fold) and higher SOC contents (1.6-fold) but similar total imaged porosity and SOC stability as aggregates. In conclusion, these results clearly indicated the direct involvement of earthworms in SOC stabilization through their impact on POM and pore spatial arrangements, which may have led to prolonged SOC sequestration for > 400 d.

Holocene variation in the Indian Summer Monsoon modulated by the tropical Indian Ocean sea-surface temperature mode

The evolution of the Indian Summer Monsoon (ISM) has been widely investigated owing to its significant climatic and socioeconomic influences. However, debates remain concerning the temporal variation during the Holocene and its driving mechanisms, particularly the potential contribution of sea-surface temperature (SST) in the tropical Indian Ocean (TIO). Here, we present a continuous sediment record covering the past 11.1 kyrs from the Beihai Wetland, southwestern China. The grain size, geochemical element composition and total organic carbon content (TOC) were analyzed and interpreted in terms of the sedimentary conditions, catchment erosion and regional climate variations. Higher detrital inputs and possibly high water levels were determined during the early to mid-Holocene period, suggesting strong catchment erosion under an intensified ISM. The maximum monsoon intensity appeared between 7.5 and 5.2 cal. kyr BP, which is broadly consistent with various ISM records. We propose that such mid-Holocene monsoon strengthening was primarily triggered by the TIO SST anomaly modes, i.e., the Indian Ocean Basin (IOB) mode and the Indian Ocean dipole (IOD) mode. Based on Holocene SST records from the TIO, a positive SST anomaly (positive IOB mode) and positive zonal SST anomaly gradient (positive IOD mode) may have occurred during the mid-Holocene, which jointly triggered intensification of the ISM. Our findings emphasize the significant contribution of the TIO in modulating the summer monsoon system. The abrupt increases in TOC content and median grain size indicate the formation of the current wetland system at approximately 5.2 cal. kyr BP following the decline in regional moisture as well as the retreat of the ISM. In addition, notable human impacts were determined during the last 800 years, as indicated by intensified catchment erosion in response to human-induced deforestation.

Diurnal variability of lower and middle atmospheric water vapour over the Asian summer monsoon region: first results from COSMIC-1 and TIMED-SABER measurements

First observations on the vertical structure of diurnal variability of water vapour in the lower and middle atmosphere using 13 years of COSMIC-1 and 18 years of SABER observations over the Asian summer monsoon region are presented in this paper. The most significant and new observation is that the middle stratospheric water vapour (SWV) enhancement is observed between 9 and 18 LT, whereas it is between 6 and 15 LT near tropopause in all the seasons. The diurnal amplitude of water vapour near tropopause is between 0.3 and 0.4 ppmv. Bimodal peaks are found in the diurnal amplitude of SWV, maximizing between 25 and 30 km (~ 0.4 ppmv), and between 45 and 50 km (~ 0.6 ppmv). The analysis reveals that the diurnal variability in the lower SWV is controlled by the tropical tropopause temperature, whereas the middle and upper SWV is primarily controlled by methane oxidation. The results are presented and discussed in the light of present understanding.

Changes in Hadley circulation and intertropical convergence zone under strategic stratospheric aerosol geoengineering

Stratospheric aerosol geoengineering has been proposed as a potential solution to reduce climate change and its impacts. Here, we explore the responses of the Hadley circulation (HC) intensity and the intertropical convergence zone (ITCZ) using the strategic stratospheric aerosol geoengineering, in which sulfur dioxide was injected into the stratosphere at four different locations to maintain the global-mean surface temperature and the interhemispheric and equator-to-pole temperature gradients at present-day values (baseline). Simulations show that, relative to the baseline, strategic stratospheric aerosol geoengineering generally maintains northern winter December–January–February (DJF) HC intensity under RCP8.5, while it overcompensates for the greenhouse gas (GHG)-forced southern winter June–July–August (JJA) HC intensity increase, producing a 3.5 ± 0.4% weakening. The residual change of southern HC intensity in JJA is mainly associated with stratospheric heating and tropospheric temperature response due to enhanced stratospheric aerosol concentrations. Geoengineering overcompensates for the GHG-driven northward ITCZ shifts, producing 0.7° ± 0.1° and 0.2° ± 0.1° latitude southward migrations in JJA and DJF, respectively relative to the baseline. These migrations are affected by tropical interhemispheric temperature differences both at the surface and in the free troposphere. Further strategies for reducing the residual change of HC intensity and ITCZ shifts under stratospheric aerosol geoengineering could involve minimizing stratospheric heating and restoring and preserving the present-day tropical tropospheric interhemispheric temperature differences.

Stratospheric ozone response to sulfate aerosol and solar dimming climate interventions based on the G6 Geoengineering Model Intercomparison Project (GeoMIP) simulations

Abstract. This study assesses the impacts of stratospheric aerosol intervention (SAI) and solar dimming on stratospheric ozone based on the G6 Geoengineering Model Intercomparison Project (GeoMIP) experiments, called G6sulfur and G6solar. For G6sulfur, an enhanced stratospheric sulfate aerosol burden reflects some of the incoming solar radiation back into space to cool the surface climate, while for G6solar, the reduction in the global solar constant in the model achieves the same goal. Both experiments use the high emissions scenario of SSP5-8.5 as the baseline experiment and define surface temperature from the medium emission scenario of SSP2-4.5 as the target. In total, six Earth system models (ESMs) performed these experiments, and three out of the six models include interactive stratospheric chemistry. The increase in absorbing sulfate aerosols in the stratosphere results in a heating of the lower tropical stratospheric temperatures by between 5 to 13 K for the six different ESMs, leading to changes in stratospheric transport, water vapor, and other related changes. The increase in the aerosol burden also increases aerosol surface area density, which is important for heterogeneous chemical reactions. The resulting changes in the springtime Antarctic ozone between the G6sulfur and SSP5-8.5, based on the three models with interactive chemistry, include an initial reduction in total column ozone (TCO) of 10 DU (ranging between 0–30 DU for the three models) and up to 20 DU (between 10–40 DU) by the end of the century. The relatively small reduction in TCO for the multi-model mean in the first 2 decades results from variations in the required sulfur injections in the models and differences in the complexity of the chemistry schemes. In contrast, in the Northern Hemisphere (NH) high latitudes, no significant changes can be identified due to the large natural variability in the models, with little change in TCO by the end of the century. However, all three models with interactive chemistry consistently simulate an increase in TCO in the NH mid-latitudes up to 20 DU, compared to SSP5-8.5, in addition to the 20 DU increase resulting from increasing greenhouse gases between SSP2-4.5 and SSP5-8.5. In contrast to G6sulfur, G6solar does not significantly change stratospheric temperatures compared to the baseline simulation. Solar dimming results in little change in TCO compared to SSP5-8.5. Only in the tropics does G6solar result in an increase of TCO of up to 8 DU, compared to SSP2-4.5, which may counteract the projected reduction in SSP5-8.5. This work identifies differences in the response of SAI and solar dimming on ozone for three ESMs with interactive chemistry, which are partly due to the differences and shortcomings in the complexity of aerosol microphysics, chemistry, and the description of ozone photolysis. It also identifies that solar dimming, if viewed as an analog to SAI using a predominantly scattering aerosol, would succeed in reducing tropospheric and surface temperatures, but any stratospheric changes due to the high forcing greenhouse gas scenario, including the potential harmful increase in TCO beyond historical values, would prevail.

Low temperature and other treatments to maintain the quality of fresh-cut nopalitos

ISHS V International Conference on Postharvest and Quality Management of Horticultural Products of Interest for Tropical Regions Low temperature and other treatments to maintain the quality of fresh-cut nopalitos

A channel selection for the assimilation of CrIS and HIRAS instruments at full spectral resolution

AbstractA new channel selection is proposed for the processing of observations at full spectral resolution (FSR) from the Cross‐track Infrared Sounder (CrIS) and Hyperspectral Infrared Atmospheric Sounder (HIRAS) instruments in the Met Office global numerical weather prediction (NWP) system. The new selection has been derived in order to minimise the error in NWP analysis and has been compared to an existing selection developed at the National Oceanic and Atmospheric Administration (NOAA). Both selections have been tested in the Met Office global NWP system to investigate the use of FSR CrIS compared with the current normal spectral resolution (NSR) set‐up employed in operations. Improvements are obtained for most forecast variables up to 7‐day lead times, with change in root‐mean‐square error (RMSE) ranging from 0.13 to 0.54%, although degradation of tropical temperatures are noted for the NOAA selection. The background fit to observations from independent sounders improves by up to 0.8% with the new selection, outperforming the NOAA selection which results in degradations across most instruments. The assimilation of HIRAS observations does not however benefit the system.

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink. Dry-season climate variability is a primary driver of tropical tree growth, according to observations from a pantropical tree-ring network.

Practical eDNA sampling methods inferred from particle size distribution and comparison of capture techniques for a Critically Endangered elasmobranch

AbstractEnvironmental DNA (eDNA) methods are increasingly applied in the marine environment to identify species and community structure. To establish widely applicable eDNA techniques for elasmobranchs, we used the Critically Endangered largetooth sawfish (Pristis pristis Linnaeus, 1758) as a model species for: (1) assessing eDNA particle size distribution; (2) assessing the efficiency of long‐term preservation of water samples; and (3) comparing the efficiency and detection sensitivity of filtration and precipitation methods. Water samples (1 L) collected from a tank containing one largetooth sawfish specimen were sequentially filtered through five filter membranes of decreasing pore size (20, 10, 5, 1.2, and 0.45 μm). The proportion of sawfish eDNA retained within each size class was determined through quantitative real‐time PCR (qPCR) using a species‐specific TaqMan probe assay. A linear mixed‐effects model (lme) showed that the 1.2 and 20 µm filters captured most of the eDNA particles present in the sampled water. Additionally, whole water samples (0.375 L) were preserved in Longmire's buffer, stored at tropical ambient temperatures (26.3°C ± 3.0 SD) and extracted at five time points: immediately, one, two, and three months after collection, as well as frozen and extracted three months later, to assess the preservation efficiency of Longmire's buffer via qPCR analysis. A linear mixed‐effects model showed that samples maintained maximal eDNA yield for at least three months after collection at ambient storage. Lastly, when comparing the filtration and precipitation methods, filtration using 0.45 µm pore size was more sensitive to capture of largetooth sawfish eDNA than filtration with 20 µm filter or water precipitation. However, water precipitation was more efficient when accounting for volume of water processed. These results provide options for best capture and preservation of elasmobranch eDNA.

Tropical extreme droughts drive long-term increase in atmospheric CO2 growth rate variability

The terrestrial carbon sink slows the accumulation of carbon dioxide (CO2) in the atmosphere by absorbing roughly 30% of anthropogenic CO2 emissions, but varies greatly from year to year. The resulting variations in the atmospheric CO2 growth rate (CGR) have been related to tropical temperature and water availability. The apparent sensitivity of CGR to tropical temperature ({{{{{{rm{gamma }}}}}}}_{{{{{{rm{CGR}}}}}}}^{{{{{{rm{T}}}}}}}) has changed markedly over the past six decades, however, the drivers of the observation to date remains unidentified. Here, we use atmospheric observations, multiple global vegetation models and machine learning products to analyze the cause of the sensitivity change. We found that a threefold increase in {{{{{{rm{gamma }}}}}}}_{{{{{{rm{CGR}}}}}}}^{{{{{{rm{T}}}}}}} emerged due to the long-term changes in the magnitude of CGR variability (i.e., indicated by one standard deviation of CGR; STDCGR), which increased 34.7% from 1960-1979 to 1985-2004 and subsequently decreased 14.4% in 1997-2016. We found a close relationship (r2 = 0.75, p < 0.01) between STDCGR and the tropical vegetated area (23°S – 23°N) affected by extreme droughts, which influenced 6-9% of the tropical vegetated surface. A 1% increase in the tropical area affected by extreme droughts led to about 0.14 Pg C yr−1 increase in STDCGR. The historical changes in STDCGR were dominated by extreme drought-affected areas in tropical Africa and Asia, and semi-arid ecosystems. The outsized influence of extreme droughts over a small fraction of vegetated surface amplified the interannual variability in CGR and explained the observed long-term dynamics of {{{{{{rm{gamma }}}}}}}_{{{{{{rm{CGR}}}}}}}^{{{{{{rm{T}}}}}}}.