Clear Diurnal Variation Research Articles

Resolving Atmospheric Oxygenated Organic Molecules in Urban Beijing Using Online Ultrahigh-Resolution Chemical Ionization Mass Spectrometry.

Gaseous oxygenated organic molecules (OOMs) are crucial precursors of atmospheric organic aerosols. OOMs in urban atmospheres have complex compositions, posing challenges to understanding their formation, evolution, and influences. In this study, we identify 2403 atmospheric gaseous OOMs in urban Beijing using online nitrate-based chemical ionization Orbitrap mass spectrometry based on one-year atmospheric measurements. We find that OOMs in urban atmospheres can be identified with higher accuracy and wider coverage, compared to previously used online mass spectrometry. With optimized OOM resolving capabilities, previous knowledge of OOMs in urban atmospheres can be expanded. First, clear homologous and oxygen-addition characteristics of the OOMs are revealed. Second, OOMs with lower concentrations or higher masses are identified and characterized with high confidence, e.g., OOMs with masses above 350 Da. In particular, dimers of OOMs (e.g., C20H32O8-15N2), crucial species for organic nucleation, are identified. During four seasons, nitrogen-containing OOMs dominate the total concentration of OOMs, and OOMs are mainly from aromatic and aliphatic oxidation. Additionally, radicals with similar composition as OOMs, intermediates for OOM formation, are identified with clear diurnal variation, e.g., CnH2n-5O6 radicals (n = 8-10) and CmH2m-4NO9 radicals (m = 9-10), peak during the daytime and nighttime, respectively, previously having scarce measurement evidence in urban atmospheres.

Periodic Oscillation of VLF Transmitter Signals Measured in Low and Middle Latitude Regions

AbstractMeasurements of Very Low Frequency (VLF) signals from navy transmitters carry direct information about the D‐region ionosphere and have been widely utilized for detecting the electron density at D‐region altitudes, but not frequently for the atmospheric waves therein. Atmospheric waves have been extensively studied using the total ionospheric electron content, but if and how they are correlated with the D‐region ionosphere and VLF measurements still remains poorly investigated. In this study, we have conducted a comprehensive analysis using 7‐year measurements (2016–2022) of VLF signals from the JJI, NWC, and VTX transmitters as being recorded in Suizhou, China. These three transmitter‐receiver paths are representative and the corresponding observations constitute a valuable data set to investigate the periodicities of VLF data. Different from previous studies, we have utilized the ensemble empirical mode decomposition and Lomb‐Scargle methods to determine the periodicities of these data. By contrasting these paths, prominent periodicities ranging from 2 to 730 days have been found, with clear diurnal variation and suggestive latitudinal/longitudinal dependence. Moreover, we have found that the mesospheric temperature is closely related with the annual oscillation of VLF measurements, while this oscillation has a low correlation with solar Lyman‐α fluxes or geomagnetic activity. The oscillations with relatively shorter periods are likely atmospheric waves such as gravity waves, planetary waves, or harmonics of these waves. Our results suggest that, in addition to the electron density, the subionospheric VLF technique can be potentially utilized to remotely sense atmospheric waves that propagate up to or through the D‐region ionosphere.

Cloud Characteristics in South China Using Ka-Band Millimeter Cloud Radar Datasets

In this study, we investigate the seasonal and diurnal variations in cloud occurrence frequency, as well as cloud vertical structure (CVS) characteristics under different seasons and precipitation intensities over the Guangzhou region in South China, based on the analysis of millimeter-wave cloud radar (MMCR) and ground automatic weather station rainfall observations from May 2019 to August 2021. The results showed that the occurrence frequency of clouds exhibits a bimodal distribution throughout the year, with peaks in March to June and October, reaching its highest occurrence in May at approximately 80% and its lowest from December to February at around 40%. Additionally, there are distinct diurnal variations in occurrence frequency, with the lowest rates occurring around 0005 LST, rapidly increasing after 0006 LST, and peaking during the afternoon to evening hours. Cloud top height (CTH) shows bimodal distributions during the pre-flood and post-flood seasons. The most frequently occurring range of CTH during the pre-flood season is below 3 km, accounting for approximately 43%, while during the post-flood season, it ranges from 11 to 14 km, constituting about 37%. For precipitation clouds, CTH can extend beyond 12 km, with the radar reflectivity decreasing gradually with increasing height. The highest frequencies of radar echoes are observed below 2 km and between 4 and 7 km, exhibiting clear diurnal variations, with echoes mainly below 2 km and between 4 to 6 km during the early morning, intensifying and shifting to higher altitudes during the day and reaching their maximum below 4 km during the afternoon to nighttime hours, while both the frequency and intensity increase in the height range of 4 to 12 km. Vertical profiles of radar reflectivity and cloud ice/liquid water content (IWC/LWC) exhibit similar trends under different precipitation intensities. The main differences are observed below 4 km, where both radar reflectivity and IWC/LWC generally increase with increasing precipitation intensity. These findings contribute to a better understanding of cloud characteristics in the South China region, enhance the accuracy of model simulations, and provide a scientific basis for accurate forecasting and warning of meteorological disasters.

A GEO-GEO Stereo Observation of Diurnal Cloud Variations over the Eastern Pacific

Fast atmospheric processes such as deep convection and severe storms are challenging to observe and understand without adequate spatiotemporal sampling. Geostationary (GEO) imaging has the advantage of tracking these fast processes continuously at a cadence of the 10 min global and 1 min mesoscale from thermal infrared (TIR) channels. More importantly, the newly-available GEO-GEO stereo observations from our 3D-Wind algorithm provide more accurate height assignment for atmospheric motion vectors (AMVs) than those from conventional TIR methods. Unlike the radiometric methods, the stereo height is insensitive to radiometric TIR calibration of satellite sensors and can assign the feature height correctly under complex situation (e.g., multi-layer clouds and atmospheric inversion). This paper shows a case study from continuous GEO-GEO stereo observations over the Eastern Pacific during 1–5 February 2023, to highlight diurnal variations of clouds and dynamics in the planetary boundary layer (PBL), altocumulus/congestus, convective outflow and tropical tropopause layer (TTL). Because of their good vertical resolution, the stereo observations often show a wind shear in these cloud layers. As an example, the stereo winds reveal the classic Ekman spiral in marine PBL dynamics with a clockwise (counterclockwise) wind direction change with height in the Northern (Southern) Hemisphere subtropics. Over the Southeastern Pacific, the stereo cloud observations show a clear diurnal variation in the closed-to-open cell transition in the PBL and evidence of precipitation at a lower level from broken stratocumulus clouds.

Variability of corticospinal and spinal reflex excitability for the ankle dorsiflexor tibialis anterior across repeated measurements in people with and without incomplete spinal cord injury

To adequately evaluate the corticospinal and spinal plasticity in health and disease, it is essential to understand whether and to what extent the corticospinal and spinal responses fluctuate systematically across multiple measurements. Thus, in this study, we examined the session-to-session variability of corticospinal excitability for the ankle dorsiflexor tibialis anterior (TA) in people with and without incomplete spinal cord injury (SCI). In neurologically normal participants, the following measures were obtained across 4 days at the same time of day (N = 13) or 4 sessions over a 12-h period (N = 9, at 8:00, 12:00, 16:00, and 20:00): maximum voluntary contraction (MVC), maximum M-wave and H-reflex (Mmax and Hmax), motor evoked potential (MEP) amplitude, and silent period (SP) after MEP. In participants with chronic incomplete SCI (N = 17), the same measures were obtained across 4 days. We found no clear diurnal variation in the spinal and corticospinal excitability of the TA in individuals with no known neurological conditions, and no systematic changes in any experimental measures of spinal and corticospinal excitability across four measurement days in individuals with or without SCI. Overall, mean deviations across four sessions remained in a range of 5–13% for all measures in participants with or without SCI. The study shows the limited extent of non-systematic session-to-session variability in the TA corticospinal excitability in individuals with and without chronic incomplete SCI, supporting the utility of corticospinal and spinal excitability measures in mechanistic investigation of neuromodulation interventions. The information provided through this study may serve as the reference in evaluating corticospinal plasticity across multiple experimental sessions.

Vertical distribution of black carbon and its mixing state in the urban boundary layer in summer

Abstract. The vertical distribution of black carbon (BC), as well as its mixing state, is of great concern due to BC's strong regional climatic and environmental effects. In this study, vertical measurements were conducted through a moveable container based on a meteorological tower in the Beijing urban area during June and July. A total of 112 vertical profiles (0–240 m), including the concentrations of BC, O3, NOx and the optical properties of aerosols, were obtained. Based on BC concentration, the vertical profiles could be classified into four categories: uniform, gradual decrease, sharp decrease and sudden increase. The uniform type indicates strong vertical mixing with similar pollutant concentrations along the vertical direction. The gradual and sharp decrease types indicate stable vertical conditions with higher pollutant concentrations on the ground and lower concentrations at higher altitudes. Due to the strong radiation in summer, the vertical profiles exhibited a clear diurnal variation in which ∼ 80 % of profiles were uniform during the daytime and ∼ 40 %–90 % of profiles were of the gradual and sharp decrease types at night. O3 is an exception, and its concentration generally increases with height, even under strong vertical mixing conditions. The size distribution of the BC core varied slightly along the vertical direction, and the coating thickness, denoted by the diameter ratio between the BC-containing particle and BC core (Dp/Dc), of BC increased with height under stable conditions. Although the coating thickness could increase the absorption ability with an average absorption enhancement of 1.25 at 23:00 LT (local time: UTC+8), the vertical difference of Dp/Dc (2 %) was much lower than that of BC concentration (∼ 35 %). The vertical variation in absorption ability was mainly caused by the variation in BC concentration. In addition, O3 and Dp/Dc occasionally increased during 06:00–08:00 but remained stable during 08:00–10:00. Vertical mixing and transportation from upper heights, such as the residual layer, could significantly influence the pollutant properties on the surface during early mornings. This study exhibits a continuous vertical picture of BC and its mixing state in urban areas, which would be helpful for understanding BC's regional environmental effect.

An Observational Constraint of VOC Emissions for Air Quality Modeling Study in the Pearl River Delta Region

AbstractVolatile organic compounds (VOCs) have crucial influences on atmospheric chemistry. Accurate quantification of the VOC emissions is critical for air pollution research, especially when applying to air quality models. However, current bottom‐up emission inventories have biases, making observational constraints of VOC emissions necessary. We conducted concurrent VOC measurements in the Pearl River Delta (PRD) region during the summer of 2018 and found large discrepancies in the spatiotemporal variations of VOCs between observations and model simulations when using the priori VOC emission inventory (Multi‐resolution Emission Inventory for China). The normalized biases of total VOC concentrations ranged from −55% to 85% across the PRD cities in the study period. To improve the simulations, we constrained the anthropogenic VOC emissions based on their measured concentrations. The observation‐constrained VOC emissions showed clear diurnal variations and resolved the spatially‐concentrated priori emissions by reducing the high emissions by 15%–36% in the central PRD cities while elevating the sparse emissions in other cities. After employing the observation‐constrained VOC emissions, the model better reproduced the spatiotemporal variations of VOCs in the PRD region, alleviating the biases to −13%–13%. Furthermore, simulations of peak ozone (O3) concentrations were amended to reduce the mean normalized bias by 5%–12% on high O3 days. Our work has effectively combined VOC field measurements with air quality modeling to achieve better simulations of VOCs and O3. Besides, the observational‐constrained emissions are flexible for studying short‐term emission changes and their subsequent impacts on air quality.

Measurement report: Molecular-level investigation of atmospheric cluster ions at the tropical high-altitude research station Chacaltaya (5240 m a.s.l.) in the Bolivian Andes

Abstract. Air ions are the key components for a series of atmospheric physicochemical interactions, such as ion-catalyzed reactions, ion-molecule reactions, and ion-induced new particle formation (NPF). They also control atmospheric electrical properties with effects on global climate. We performed molecular-level measurements of cluster ions at the high-altitude research station Chacaltaya (CHC; 5240 m a.s.l.), located in the Bolivian Andes, from January to May 2018 using an atmospheric-pressure-interface time-of-flight mass spectrometer. The negative ions mainly consisted of (H2SO4)0–3⚫HSO4-, (HNO3)0–2⚫NO3-, SO5-, (NH3)1–6⚫(H2SO4)3–7⚫HSO4-, malonic-acid-derived, and CHO / CHON⚫(HSO4- / NO3-) cluster ions. Their temporal variability exhibited distinct diurnal and seasonal patterns due to the changes in the corresponding neutral species' molecular properties (such as electron affinity and proton affinity) and concentrations resulting from the air masses arriving at CHC from different source regions. The positive ions were mainly composed of protonated amines and organic cluster ions but exhibited no clear diurnal variation. H2SO4–NH3 cluster ions likely contributed to the NPF process, particularly during the wet-to-dry transition period and the dry season, when CHC was more impacted by air masses originating from source regions with elevated SO2 emissions. Our study provides new insights into the chemical composition of atmospheric cluster ions and their role in new particle formation in the high-altitude mountain environment of the Bolivian Andes.

Characteristics and degradation of organic aerosols from cooking sources based on hourly observations of organic molecular markers in urban environments

Abstract. Molecular markers in organic aerosol (OA) provide specific source information on PM2.5, and the contribution of cooking organic aerosols to OA is significant, especially in urban environments. However, the low time resolution of offline measurements limits the effectiveness when interpreting the tracer data, the diurnal variation in cooking emissions and the oxidation process. In this study, we used online thermal desorption aerosol gas chromatography and mass spectrometry (TAG) to measure organic molecular markers in fine particulate matter (PM2.5) at an urban site in Changzhou, China. The concentrations of saturated fatty acids (sFAs), unsaturated fatty acids (uFAs) and oxidative decomposition products (ODPs) of unsaturated fatty acids were measured every 2 h to investigate the temporal variations and the oxidative decomposition characteristics of uFAs in urban environments. The average concentration of total fatty acids (TFAs, sum of sFAs and uFAs) was measured to be 105.70±230.28 ng m−3. The average concentration of TFAs in the polluted period (PM2.5≥35 µg m−3) was 147.06 ng m−3, which was 4.2 times higher than that in the clean period (PM2.5<35 µg m−3) and higher than the enhancement of PM2.5 (2.2 times) and organic carbon (OC) (2.0 times) concentrations when comparing the polluted period to the clean period. The mean concentration of cooking aerosol in the polluted period (4.0 µg m−3) was about 5.3 times higher than that in the clean period (0.75 µg m−3), which was similar to the trend of fatty acids. Fatty acids showed a clear diurnal variation. Linoleic acid / stearic acid and oleic acid / stearic acid ratios were significantly higher at dinnertime and closer to the cooking source profile. By performing backward trajectory clustering analysis, under the influence of short-distance air masses from surrounding areas, the concentrations of TFAs and PM2.5 were relatively high, while under the influence of air masses from easterly coastal areas, the oxidation degree of uFAs emitted from local culinary sources was higher. The effective rate constants (kO) for the oxidative degradation of oleic acid were estimated to be 0.08–0.57 h−1, which were lower than kL (the estimated effective rate constants of linoleic acid, 0.16–0.80 h−1). Both kO and kL showed a significant positive correlation with O3, indicating that O3 was the main nighttime oxidant for uFAs in the city of Changzhou. Using fatty acids as tracers, cooking was estimated to contribute an average of 4.6 % to PM2.5 concentrations, increasing to 7.8 % at 20:00 UTC+8 h. Cooking was an important source of OC, contributing 8.1 %, higher than the contribution of PM2.5. This study investigates the variation in the concentrations and oxidative degradation of fatty acids and corresponding oxidation products in ambient air, which can be a guide for the refinement of aerosol source apportionment and provide scientific support for the development of cooking source control policies.

The association between time of in hospital cardiac arrest and mortality; a retrospective analysis of two UK databases

AimsThe incidence of in hospital cardiac arrest (IHCA) varies throughout the day. This study aimed to report the variation in incidence of IHCA, presenting rhythm and outcome based on the hour in which IHCA occurred. MethodsWe conducted a retrospective analysis of the National Cardiac Arrest Audit (NCAA) including patients who suffered an IHCA from 1st April 2011 to 31st December 2019. We then linked the NCAA and intensive care Case Mix Programme databases to explore the effect of time of IHCA on hospital survival in the subgroup of patients admitted to intensive care following IHCA. ResultsWe identified 115,690 eligible patients in the NCAA database. Pulseless electrical activity was the commonest presenting rhythm (54.8%). 66,885 patients died in the immediate post resuscitation period. Overall, hospital survival in the NCAA cohort was 21.3%.We identified 13,858 patients with linked ICU admissions in the Case Mix Programme database; 37.0% survived to hospital discharge. The incidence of IHCA peaked at 06.00. Rates of return of spontaneous circulation, survival to hospital discharge and good neurological outcome were lowest between 05.00 and 07.00. Among those admitted to ICU, no clear diurnal variation in hospital survival was seen in the unadjusted or adjusted analysis. This pattern was consistent across all presenting rhythms. ConclusionsWe observed higher rates of IHCA, and poorer outcomes at night. However, in those admitted to ICU, this variation was absent. This suggests patient factors and processes of care issues contribute to the variation in IHCA seen throughout the day.

Influence of aerosol physicochemical properties on CCN activation during the Asian winter monsoon at the summit of Mt. Lu, China

To better understand the characteristics of high-altitude aerosol (or condensation nuclei, CN) and cloud condensation nuclei (CCN) in East China during the Asian winter monsoon, a field campaign focused on aerosol and CCN was set up in the area of Mt. Lu during the period from 5 November to 10 December 2019. The features of CCN and CCN formation at Mt. Lu were analyzed. The CCN spectra at Mt. Lu belongs to a polluted continental type, which could be parameterized using N = 2498S0.31, with S denoting supersaturation. The average and standard deviation of the CCN (S = 0.4%) and CN concentrations were 1936 ± 1007 cm−3 and 3041 ± 1646 cm−3, respectively. The CCN activation fraction (AF) values are 0.43, 0.57, 0.64, 0.69, and 0.72 at S = 0.2%, S = 0.4%, S = 0.6%, S = 0.8% and S = 1%, respectively. The aerosol composition would be more important than aerosol size in determining CCN activation at Mt. Lu. The CCN (CN) number concentration had a clear diurnal variation with maximal and minimal values at 13:00 (12:00 and 18:00) and 07:00 (07:00), respectively. Nearly 68.7% of the air mass reaching Mt. Lu came from the northern area. The higher-sulfate-ratio air mass has a relatively high AF efficiency.

Water use strategies of Ferula bungeana on mega-dunes in the Badain Jaran Desert.

In desert ecosystems, ephemeral plants have developed specialized water use strategies in response to long-term natural water stress. To examine the water use strategies of desert ephemeral plants under natural extreme drought conditions, we investigated the water absorption sources, water potential, hydraulic conductivity, and water use efficiency of Ferula bungeana at different elevations on the slopes of mega-dunes in the Badain Jaran Desert, Inner Mongolia, during a period of extreme drought. We found that the water utilized by F. bungeana was mostly absorbed from the 0-60 cm soil layers (80.47 ± 4.28%). With progression of the growing season, the source of water changed from the 0-30 cm soil layer to the 30-60cm layer. The water potentials of the leaves, stems, and roots of F. bungeana were found to be characterized by clear diurnal and monthly variation, which were restricted by water availability and the hydraulic conductivity of different parts of the plant. The root hydraulic conductivity of F. bungeana was found to be considerably greater than that of the canopy, both of which showed significant diurnal and monthly variation. The water use efficiency of F. bungeana under extreme drought conditions was relatively high, particularly during the early and late stages of the growing season. Variations in water availability led to the regulation of water uptake and an adjustment of internal water conduction, which modified plant water use efficiency. These observations tend to indicate that the water use strategies of F. bungeana are mainly associated with the growth stage of plants, whereas the distribution pattern of plants on mega-dunes appeared to have comparatively little influence. Our findings on the water use of ephemeral plants highlight the adaptive mechanisms of these plants in desert habitats and provide a theoretical basis for selecting plants suitable for the restoration and reconstruction of desert ecosystems.

Sensitivity of Ozone Formation in Summer in Jinan Using Observation-Based Model

According to online monitoring data on atmospheric ozone and the pollution characteristics of its precursors obtained in Jinan in June 2021, we analyzed different sites: urban sites (city monitoring station, Quancheng Square), an industrial park site (oil refinery), and a suburban site (Paomaling). The relative incremental reactivity of different precursors was calculated using a photochemical observation-based model to explore the sensitivity of O3 generation at each site and to draw a curve using the empirical kinetics modeling approach. The PMF model was used to analyze the origin of volatile organic compounds (VOCs) pollution in Jinan. The results showed that the concentration of O3 at the industrial park was higher than that in the urban area in Jinan, which may be related to the fact that ozone precursor concentrations in the industrial park were significantly higher than those in the urban area (the AVOCs concentration at the industrial park site was 56.9 ppbv, approximately twice that of the urban site), and there are emission peaks at night; alkanes, oxygenated compounds, and halogenated hydrocarbons were the main components of the AVOCs, and olefins, alkanes, and aromatic hydrocarbons were the main active components in Jinan. The O3 generation in urban areas generally occurred in the VOCs-sensitive zones, while the O3 generation in the other areas occurred in the VOCs-NOx transition zone; there was a clear diurnal variation in the sensitivity of the industrial park, with the site being in the obvious VOCs-sensitive zone from nighttime to morning hours and shifting to the VOCs-NOx transition zone in the afternoon hours; the relative incremental reactivity (RIR) value of AVOCs for O3 generation in Jinan was the largest, and olefins were the most sensitive component of O3. The AVOCs in Jinan mainly originated from motor vehicle exhaust, oil and gas volatilization, industrial emissions, and solvent use, and ozone prevention and control in summer should strengthen the control of these sources.

Ensemble-based diurnally varying background error covariances and their impact on short-term weather forecasting

Background error covariance (BEC) plays an essential role in variational data assimilation. Most variational data assimilation systems still use static BEC. Actually, the characteristics of BEC vary with season, day, and even hour of the background. National Meteorological Center–based diurnally varying BECs had been proposed, but the diurnal variation characteristics were gained by climatic samples. Ensemble methods can obtain the background error characteristics that suit the samples in the current moment. Therefore, to gain more reasonable diurnally varying BECs, in this study, ensemble-based diurnally varying BECs are generated and the diurnal variation characteristics are discussed. Their impacts are then evaluated by cycling data assimilation and forecasting experiments for a week based on the operational China Meteorological Administration-Beijing system. Clear diurnal variation in the standard deviation of ensemble forecasts and ensemble-based BECs can be identified, consistent with the diurnal variation characteristics of the atmosphere. The results of one-week cycling data assimilation and forecasting show that the application of diurnally varying BECs reduces the RMSEs in the analysis and 6-h forecast. Detailed analysis of a convective rainfall case shows that the distribution of the accumulated precipitation forecast using the diurnally varying BECs is closer to the observation than using the static BEC. Besides, the cycle-averaged precipitation scores in all magnitudes are improved, especially for the heavy precipitation, indicating the potential of using diurnally varying BEC in operational applications.摘要背景场误差协方差在资料同化系统中具有非常重要的作用, 目前业务变分同化系统中常采用静态背景场误差协方差, 未考虑其具体的日变化特征. 为构建更为合理且便于业务系统应用的日变化背景误差协方差, 本文构建了高分辨率集合预报样本的日变化背景场误差协方差, 揭示了其日变化特征, 并应用到了CMA-BJ业务系统中, 开展了基于业务框架的批量循环同化预报试验. 结果表明, 背景场误差存在明显的日变化特征, 采用集合日变化背景场误差协方差能够改进模式的预报效果.

Ground-Based MAX-DOAS Measurements of Tropospheric Aerosols, NO2, and HCHO Distributions in the Urban Environment of Shanghai, China

Aerosol extinction profiles at 550 nm were retrieved by applying multi-axis differential optical absorption spectroscopy (MAX-DOAS) and lookup table. Then the tropospheric NO2 and HCHO vertical column densities were retrieved using a two-step method from 28 July to 5 August of 2015 in Shanghai. The retrieved results were compared with the satellite products, and then their diurnal variation was observed. A consistency check was performed before the inversion to obtain a correction factor. Based on the sensitivity of geometric angles to oxygen dimer air mass factor (O4 AMF, AMF is the ratio of the slanted column density to the vertical column density), the parameterization scheme of geometric angles in the lookup table is optimized. The results show that the aerosol increased significantly in the afternoon. The diurnal variation of tropospheric NO2 and HCHO vertical column densities (VCDs) are bimodal and unimodal patterns respectively, and their values are higher than those of GOME-2 and OMI satellite products. A process of aerosol reduction and recovery are related to ground particulates and meteorological elements. The chemical sensitivity of local ozone production also has a clear diurnal variation.

Seasonal to sub-seasonal variations of the Asian Tropopause Aerosols Layer affected by the deep convection, surface pollutants and precipitation

The Asian Tropopause Aerosols Layer (ATAL) refers to an accumulation of aerosols in the upper troposphere and lower stratosphere during boreal summer over Asia, which has a fundamental impact on the monsoon system and climate change. In this study, we primarily analyze the seasonal to sub-seasonal variations of the ATAL and the factors potentially influencing those variations based on MERRA2 reanalysis. The ability of the reanalysis to reproduce the ATAL is well validated by CALIPSO observations from May to October 2016. The results reveal that the ATAL has a synchronous spatiotemporal pattern with the development and movement of the Asian Summer Monsoon. Significant enhancement of ATAL intensity is found during the prevailing monsoon period of July–August, with two maxima centered over South Asia and the Arabian Peninsula. Owing to the fluctuations of deep convection, the ATAL shows an episodic variation on a timescale of 7–12 days. Attribution analysis indicates that deep convection dominates the variability of the ATAL with a contribution of 62.7%, followed by a contribution of 36.6% from surface pollutants. The impact of precipitation is limited. The ATAL further shows a clear diurnal variation: the peak of ATAL intensity occurs from 17:30 to 23:30 local time (LT), when the deep convection becomes strongest; the minimum ATAL intensity occurs around 8:30 LT owing to the weakened deep convection and photochemical reactions in clouds. The aerosol components of the ATAL show different spatiotemporal patterns and imply that black carbon and organic carbon come mainly from India, whereas sulfate comes mainly from China during the prevailing monsoon period.

Measurement report: Long-term measurements of aerosol precursor concentrations in the Finnish subarctic boreal forest

Abstract. Aerosol particles form in the atmosphere via the clustering of certain atmospheric vapors. After growing into larger particles by the condensation of low-volatility gases, they can affect the Earth's climate by scattering light and acting as cloud condensation nuclei (CCN). Observations of low-volatility aerosol precursor gases have been reported around the world, but longer-term measurement series and any Arctic data sets showing seasonal variation are close to nonexistent. Here, we present ∼7 months of aerosol precursor gas measurements performed with a nitrate-based chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer. We deployed our measurements ∼150 km north of the Arctic Circle at the SMEAR I (Station for Measuring Ecosystem–Atmosphere Relations) continental Finnish subarctic field station, located in the Värriö strict nature reserve. We report concentration measurements of the most common compounds related to new particle formation (NPF): sulfuric acid (SA), methane sulfonic acid (MSA), iodic acid (IA) and the total concentration of highly oxygenated organic molecules (HOMs). At this remote measurement site, SA originates from both anthropogenic and biological sources and has a clear diurnal cycle but no significant seasonal variation. MSA shows a more distinct seasonal cycle, with concentrations peaking in the summer. Of the measured compounds, IA concentrations are the most stable throughout the measurement period, except in April during which time the concentration of IA is significantly higher than during the rest of the year. Otherwise, IA has almost identical daily maximum concentrations in spring, summer and autumn, and on NPF event or non-event days. HOMs are abundant during the summer months and low in the autumn months. Due to their low autumn concentrations and high correlation with ambient air temperature, we suggest that most HOMs are products of biogenic emissions, most probably monoterpene oxidation products. NPF events at SMEAR I happen under relatively low-temperature (1–8 ∘C) conditions, with a fast temperature rise in the early morning hours as well as lower and decreasing relative humidity (RH, 55 % vs. 80 %) during NPF days compared with non-event days. NPF days have clearly higher global irradiance values (∼450 m−2 vs. ∼200 m−2) and about 10 ppbv higher ozone concentrations than non-event days. During NPF days, we have, on average, higher SA concentrations, peaking at noon; higher MSA concentrations in the afternoon; and slightly higher IA concentration than during non-event days. In summary, these are the first long-term measurements of aerosol-forming vapors from SMEAR I in the subarctic region, and the results of this work will help develop an understanding of atmospheric chemical processes and aerosol formation in the rapidly changing Arctic.

Multi Field Coupled Coseismic Changes of the Jiashi Ms = 6.4 Earthquake of 19 January 2020, Based on Ground Temperature Observation

The coseismic geothermal changes of ground temperature observed at observatories near the epicenter of the 2020 Jiashi Ms = 6.4 earthquake in China, provide a unique opportunity to study heat generation and conduction in rock. Here, evolutions of rock temperature at the Xikeer, Jiashizongchang, and Gedaliang observatories, which are located at epicentral distances of 1.4, 27.42, and 50 km respectively, were analyzed. Significant coseismic geothermal changes of 0.0432 °C were observed at the Xikeer observatory at the depth of 33.38 m, at which clear diurnal variations can be observed. Smaller changes of ~0.0001 °C were observed at the depths of 12.3 and 22.8 m at the Xikeer observatory and 22.3 m at the Jiashizongchang observatory. The stress transfer induced by the coseismic rupture induced a rise in local ground temperature, but the magnitude of the change was relatively small. The larger amplitude change at the Xikeer observatory was caused by fluid infiltration. We note that diurnal variation has been recorded at the Gedaliang observatory, but the coseismic response is no longer in existence. The temperature increases at the hypocentral area were higher than expected in the ground due to the coseismic stress transfer, but the change attenuated rapidly with distance.

Environmental Controls on Multi-Scale Dynamics of Net Carbon Dioxide Exchange From an Alpine Peatland on the Eastern Qinghai-Tibet Plateau.

Peatlands are characterized by their large carbon storage capacity and play an essential role in the global carbon cycle. However, the future of the carbon stored in peatland ecosystems under a changing climate remains unclear. In this study, based on the eddy covariance technique, we investigated the net ecosystem CO2 exchange (NEE) and its controlling factors of the Hongyuan peatland, which is a part of the Ruoergai peatland on the eastern Qinghai-Tibet Plateau (QTP). Our results show that the Hongyuan alpine peatland was a CO2 sink with an annual NEE of −226.61 and −185.35 g C m–2 in 2014 and 2015, respectively. While, the non-growing season NEE was 53.35 and 75.08 g C m–2 in 2014 and 2015, suggesting that non-growing seasons carbon emissions should not be neglected. Clear diurnal variation in NEE was observed during the observation period, with the maximum CO2 uptake appearing at 12:30 (Beijing time, UTC+8). The Q10 value of the non-growing season in 2014 and 2015 was significantly higher than that in the growing season, which suggested that the CO2 flux in the non-growing season was more sensitive to warming than that in the growing season. We investigated the multi-scale temporal variations in NEE during the growing season using wavelet analysis. On daily timescales, photosynthetically active radiation was the primary driver of NEE. Seasonal variation in NEE was mainly driven by soil temperature. The amount of precipitation was more responsible for annual variation of NEE. The increasing number of precipitation event was associated with increasing annual carbon uptake. This study highlights the need for continuous eddy covariance measurements and time series analysis approaches to deepen our understanding of the temporal variability in NEE and multi-scale correlation between NEE and environmental factors.

Neonatal adjustments in respiratory and pulse rates in tropical breeds of buck-kids and doelings

BackgroundThe transition to pulmonary respiration and the termination of foetal cardiovascular shunts is expected to commence immediately after birth. Subsequently, alveolar ventilation and tissue perfusion must be established, despite the challenge of extra-uterine environmental conditions, which could be quite demanding, even to the adult animals. The current study evaluated neonatal adjustment and diurnally induced changes in respiratory and pulse rates in kids of Red Sokoto, Sahel and West African Dwarf (WAD) goats in a tropical climate.ResultsMorning and afternoon respiratory rates started decreasing (P < 0.05) in the second week of birth. The pulse rate in the morning hours rose (P < 0.05) on Day 1 with no significant fluctuation subsequently, while the pattern in the afternoon hours showed a progressive decrease (P < 0.05) after birth. Apart from the day of birth, respiratory rate on other days increased significantly from morning to afternoon hours. The afternoon pulse rate was higher (P < 0.05) on the day of birth, but lower (P < 0.05) on Day 2 as compared to the morning values; and no diurnal difference was observed in subsequent days. The WAD goats had significantly higher respiratory and pulse rates than Red Sokoto and Sahel kids, especially in the afternoon hours. Similarly, the values were higher (P < 0.05) in doelings than buck-kids during the morning hours. The correlation between respiratory and pulse rates was positive (P < 0.05) and the strength of the association increased with age.ConclusionIt was concluded that the afternoon rise in ambient temperature induced the establishment of a clear diurnal variation in respiratory rate 24 h postnatal, while the diurnal variation in pulse rate was weak and irregular. The tropical climate may be quite challenging to the attainment of physiological stability in respiratory and cardiovascular functions of neonatal goat kids, especially during the hot season.