bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation from meteorological drought to hydrological drought on the Loess Plateau, China
Authors: Wu Jingwen , Miao Chiyuan
Published: March 2020

Drought is the most recurrent and destructive hazard in arid and semi-arid regions, and will only become more complex under climate change. It is vital to characterize the various types of drought, to investigate the potential factors affecting different types of drought, and to assess the relationship between drought types. In this study, the Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI) were used to characterize meteorological and hydrological drought, respectively, and used to investigate drought characteristics and mechanisms in 17 catchments on the Loess Plateau from 1961–2013. Furthermore, the propagation time from meteorological to hydrological drought was explored and the potential factors influencing drought propagation time were investigated. The results indicate that the Loess Plateau has experienced an increased tendency towards both meteorological and hydrological droughts over the period 1961−2013, with hydrological drought more serious than meteorological drought at various drought assessment time scales. Moreover, average drought duration and severity were greater for hydrological drought than meteorological drought. Maximum 5-day precipitation (Rx5day) was the dominant extreme climate index for explaining variance in meteorological drought at the annual time scale. Owing to the greater complexity underlying hydrological drought, Rx5day, the number of warm days (Tx90p), and the number of warm nights (Tn90p) all contribute to the variance in hydrological drought. Furthermore, the percentage of forested land had a significant positive association (p<0.001) with propagation time, whereas the percentage of land given over to pasture had a significant negative association (p<0.001) with propagation time.
Studying the ionospheric absorption during large solar flare events in September 2017
Authors: Buzas Attila , Barta Veronika , Kouba Daniel
Published: March 2020

The most intense external force affecting the ionosphere from above is related to large solar flare events, therefore it is of particular importance to study their impact on the ionosphere. During solar flares, the suddenly increased radiation causes increased ionization and enhanced absorption of radio waves leading to partial or even total radio fade-out lasting for hours in some cases (e. g. [1] [2]).

 

The ionospheric response to large solar flares have been investigated using the ionosonde data measured at Pruhonice (PQ052, 50°, 14.5°) in September 2017, the most active solar period of Solar Cycle 24. A novel method [3] to calculate and investigate the absorption of radio waves propagating in the ionosphere is used to determine the absorption during large solar flare events (M and X class). Subsequently, the absorption data are compared with the indicators derived from the fmin method (fmin, the minimum frequency is considered as a qualitative proxy for the “nondeviative” radio wave absorption occurring in the D-layer). Total and partial radio fade-out and increased values (with 2-5 MHz) of the fmin parameter were experienced during and after the intense solar flares (> M3). The combination of these two methods may prove to be an efficient approach to monitor the ionospheric response to solar flares.

 

[1] Sripathi, S., Balachandran, N., Veenadhari, B., Singh, R., and Emperumal, K.: Response of the equatorial and low-latitude ionosphere to an intense X-class solar flare (X7/2B) as observed on 09 August 2011, J. Geophys. Res.-Space, 118, 2648–2659, 2013.

[2] Barta, V., Sátori, G., Berényi, K. A., Kis, Á., and Williams, E. (2019). Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa. Annales Geophysicae, Vol. 37, No. 4, pp. 747-761

[3] Sales, G. S., 2009, HF absorption measurements using routine digisonde data, Conference material, XII. International Digisonde Forum, University of Massachusetts
A Critical Zone Approach to Carbon Fluxes in the Arctic Tundra
Authors: Giamberini Mariasilvia , Baneschi Ilaria , Lelli Matteo , Magnani Marta , Raco Brunella , Provenzale Antonello
Published: March 2020

Arctic tundra is currently undergoing significant changes induced by the effects of a rapid temperature rise, that in the Arctic is about twice as fast as in the rest of the world. The response of the system composed by the permafrost active layer, soil and vegetation is especially relevant. In fact, it is still unclear whether the system will turn from a carbon sink to a carbon source, owing to the interplay of two opposite phenomena: the increasing time span of the growing season, favouring Net Ecosystem Production (NEP), and the increasing soil temperatures, favouring degradation of organic matter through heterotrophic respiration (HR) and then creating a positive climate feedback. In this work, we analyse soil-vegetation-atmosphere CO2 flux data of a field campaign conducted in the Bayelva river basin, Spitzbergen, in the Svalbard Archipelago (NO) during summer 2019, measured by a portable accumulation chamber. We use a “Critical Zone” perspective, considering the multiple interactions between biotic and abiotic components. We measured the Net Ecosystem Exchange (NEE) and Ecosystem Respiration (ER) along a slope gradient at different degrees of soil humidity and active layer depths, relating flux data to climate and environmental parameters, soil physical-chemical parameters and vegetation type. The statistical empirical relationships between variables are analysed to identify the main drivers of carbon exchanges. An empirical data-driven model is built to describe the coupled dynamics of soil, vegetation, water and atmosphere that contributes to budgeting the carbon cycle in the Arctic Critical Zone. A comparison of the carbon fluxes obtained with the accumulation chamber method and an Eddy Covariance tower located in the same area is also addressed.
The recommended location of rain gauge stations based on radar
Authors: Kwon Taeyong , Yoon Sanghoo
Published: March 2020

The characteristics of the watershed are important to reduce hydrologic disasters, such as the risk of dam flooding. In other words, quantitative precipitation estimation(QPE) is important to manage water resources in large regions. Both radar and rain gauged data are used to improve QPE. This study is dealt with suggesting the best location of additional rain gauged stations to be installed in order to improve QPE as entropy theory. Conditional entropy is used to quantitatively evaluate the location of additional gauged stations to be installed given the existing rainfall network. Because radar produces high-resolution precipitation estimates, it can be used to identify the high entropy points to reduce rainfall uncertainty. The data were collected from May 2018 to August 2019 in the Bukhan river dam basin. Road networks were also considered for the establishment for a practical approach.

 

This work was supported by KOREA HYDRO & NUCLEAR POWER CO., LTD

(No. 2018-Tech-20)
Database of major European heat waves from 1950 to present
Authors: Lhotka Ondřej , Kyselý Jan
Published: March 2020

Europe experienced several major heat waves in the recent summers, substantially affecting human society and environment. Heat waves are generally related to joint effect of perturbed atmospheric circulation and anomalies in surface energy budget, and they are often linked to hydrological preconditioning. Contributions of these driving mechanisms, however, vary across European climatic zones. Climate models struggle to simulate the spatial differences properly, ultimately leading to large uncertainties in future heat waves’ characteristics. As the first step towards identifying spatial patterns of differences between driving mechanisms of temperature extremes, a pan-European database of observed major heat waves has been created. Heat waves are studied using the E-OBS 20.0e dataset in 0.1° horizontal grid spacing, which is analogous to that used in the ERA5 reanalysis and CORDEX regional climate models. Magnitude of heat waves is defined with respect to local daily maximum temperature (Tmax) variance, using multiples of standard deviation of Tmax summed across individual events. For each heat wave, circulation conditions and surface energy fluxes are analysed using the ERA5 reanalysis, in order to study their links to the heat wave magnitude and geographical location. In the next step, these findings are used for analyzing spatial patterns of heat wave mechanisms and as a source of reference data for evaluation of relevant processes in climate models.
Oil Pollution in the Mediterranean Sea: An Overview
Authors: Carpenter Angela
Published: March 2020

Oil pollution can enter the marine environment from many sources including land, shipping, and oil installations. It can have significant impacts on the marine environment that, depending on the type of oil, can last for prolonged periods of time. Monitoring oil pollution in the Mediterranean Sea region has been conducted using both aerial and satellite surveillance. This presentation will provide an overview of the sources and volumes of oil entering the Mediterranean, identify impacts on the marine ecosystem in general terms, and will review surveillance activities in the region, including cooperative activities undertaken by regional and EU agencies, for example.

 
Investigating future changes in Southern China precipitation characteristics based on dynamically downscaled CMIP5 climate projections
Authors: Liu Ying Lung , Tam Chi-Yung , Lee Sai Ming
Published: March 2020

In this study, general circulation model (GCM) products were dynamically downscaled using the Regional Climate Model system version 4 (RegCM4), in order to study changes in the hydrological cycle - including extreme events - due to a warmer climate by the end of the 21st century over Southern China. The performance of 22 GCMs participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating the climate over the East Asian- western north Pacific region was first evaluated. It was found that MPI-ESM-MR, CNRM-CM5, ACCESS1-3, and GFDL- CM3 can reasonably reproduce the seasonal mean atmospheric circulation in that region, as well as its interannual variability. Outputs from these GCMs were subsequently downscaled, using the RegCM4, to a horizontal resolution of 25 km × 25km, for the period of 1979 to 2003, and also from 2050 to 2099, with the latter based on GCM projection according to the RCP8.5 scenario. Results show that the whole domain would undergo warming at the lower troposphere by 3 – 4 °C over inland China and ~2 °C over the ocean and low-latitude locations. Compared to the 1979-2003 era, during 2050-2099 boreal summer, the mean precipitation is projected to increase by 1 – 2 mm/day over coastal Southern China. There is also significantly enhanced interannual variability for the same season. In boreal spring, a similar increase in both the seasonal mean and also its year-to-year variations is also found, over more inland locations at about 25°N. Extreme daily precipitation is projected to become more intense, based on analyses of the 95th percentile for these seasons. On the other hand, it will be significantly drier during autumn over a broad area in Southern China: the mean rainfall is projected to decrease by ~1 mm/day. In addition, changes in the annual number of consecutive dry days (CDD) throughout the whole calendar year was also examined. It was found that CDD over the more inland locations will increase by ~5 days. Thus, there will be a lengthening of the dry season in the region. Global warming’s potential impact on sub-daily rainfall is also examined. For the rainfall diurnal cycle (DC), there is no significant change in both spatial and temporal patterns. Moisture budget analyses are also carried out, in order to ascertain the importance of change in background moisture, versus that in wind circulation, on the intensification of MAM and JJA mean rainfall as well as their interannual variability. The implication of these results on water management and climate change adaptation over the Southern China region will be discussed.
Biogeomorphodynamic of fluvial-tidal levees and accommodation space infilling
Authors: Boechat Albernaz Marcio , Roelofs Lonneke , Pierik Harm Jan , Kleinhans Maarten
Published: March 2020

Densely populated low-lying areas are under pressure of relative sea level rise and human impacts. Low-lying areas like most of The Netherlands were built with fluvial-marine sediment supply interacting with peat and vegetation. The morphology and sedimentological architecture of such areas is controlled by initial conditions (e.g. accommodation space), boundary conditions (fluvial-tidal discharges) and internal biogeomorphodynamic feedbacks. The relative importance of these controls varies per system and we need generic rules to better understand the past and future delta and alluvial plain evolution. Here we setup novel long-term idealized morphodynamic models including stratigraphy and vegetation to unravel the effect of initial and boundary conditions in building landscape and creating complex depositional environments. Larger accommodation space creates and preserves a bayhead delta while limited space resulted in ebb-delta growth. Fluvial-tidal discharge fluctuations promote larger levees and more crevasses, contributing to floodplain accretion. The presence of sparse vegetation (i.e. trees) also contributed to floodplain infilling and created wide levees and more crevasses. On the other hand, dense vegetated floodplain inhibits levee widening and the formation of crevasses leaving the floodplain rather starved. Our results agree with the dimensions and evolution from geological reconstructions of the Rhine Delta in The Netherlands. In general, discharge fluctuations by rivers and tides, sediment delivery and (sparse) vegetation are crucial to create more land. These findings are important for the reconstruction of past environments and sediment budget estimative as well to future management of low-lying areas where raising the land-level is a challenge.
GRACE-FO accelerometer data recovery within ITSG-Grace2018 data processing
Authors: Behzadpour Saniya , Mayer-Gürr Torsten , Kvas Andreas , Krauss Sandro , Strasser Sebastian , Süsser-Rechberger Barbara
Published: March 2020

In GRACE-FO (Gravity Recovery and Climate Experiment Follow-on) mission, similar to its predecessor GRACE, the twin satellites are equipped with three-axis accelerometers, measuring the non-gravitational forces. After one month in orbit, the GRACE-D accelerometer data degraded and its measurements were replaced by synthetic accelerometer data, the so-called transplant data, officially generated by the Jet Propulsion Laboratory (JPL). The transplant data was derived from the GRACE-C accelerometer measurements, by applying a time and attitude corrections and adding model-based residual accelerations due to thruster firings on GRACE-D.

For the ITSG-Grace2018 GRACE-FO release, the gravity field recovery is based on the use of in-house Level-1B accelerometer data (ACT1B) using the provided Level-1A data products. In this work, we present a novel approach to recover the ACT1B data by (a) implementing the state-of-the-art non-gravitational force models and (b) applying additional force model corrections.

The preliminary results show the improved ACT1B data not only contributed to a noise reduction but also improved the estimates of the C20 and C30 coefficients. We show that the offset between SLR (Satellite Laser Ranging) and GRACE-FO derived C20 and C30 time series can be reduced remarkably by the use of the new accelerometer product, demonstrating the merit of this new approach.
Assessment for water resources bearing capacity based on Entropy model and EFAST weight algorithm in the Yellow River basin
Authors: Yang Libin
Published: March 2020

It is of great practical significance to analyze water resources load carry and clarify the bearing capacity of water resources in the Yellow River basin for the ecological protection and economic and social development with high quality of the Yellow River. The Entropy model and EFAST weight algorithm is coupled and employed to assess the water-resources bearing capacity in the Yellow River basin based on the double index of water quantity and quality. The results show that there are 78 groundwater overdraft areas existing, the total area and ultra-picks quantity of which is 2.26×104 km2 and 14×108 m3, respectively. Massive cones of depression are developing like Yinchuan and Dawukou in Ningxia province; Fengdong, Xinghua, Lvqiao and Weibin in Shaanxi province; Songgu, Taiyuan and Yuncheng in Shanxi province; Wuzhi, Wenxian and Mengxian in Henan province. Moreover, 47 of 70 assessed prefecture cities are in the state of overload or severe overload, in which, there are 24 severe-overload prefecture cities and the proportion is 34.3%, and the number of overload prefecture cities is 23 accounting for 32.9%. The overload and severe-overload regions concentrate in Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi and Henan provinces at the upper and middle Yellow River. In conclusion, the current water supply has exceeded its water-resources bearing capacity in the Yellow River basin. Strengthening water saving, the construction of main-stream controlled reservoirs and water diversion are the effective ways to relieve the overload state.
A simple gust estimation algorithm and machine learning based nowcasting for wind turbines
Authors: Schicker Irene , Papazek Petrina
Published: March 2020

Wind gusts and high wind speeds need to be considered in wind power industry and power grid management as they affect construction, material, siting and maintenance of turbines and power lines. Furthermore, gusts are an important information source on turbulence conditions in the atmosphere at the respective sites.
Often, the wind farm operators only provide basic data of the turbines such as average wind speed, direction, power and temperature. However, they require forecasts of gusts, too. Thus, a simple gust estimation algorithm based on the average wind speed was developed. The algorithm is tested at different mast measurement sites and WFIP2 data and applied to selected wind turbines. Results show that the algorithm is skillful enough to be used as a first guess gust estimation for single turbines and is, thus, used for nowcasting.
For nowcasting for the first two hours with a temporal fequency of ten minutes solely observations are used. A high-frequency wind speed and gust nowcasting ensemble based on different machine learning methodologies, including an ensemble for every method, was developd. Used are boosting, random forest, linear regression, a simple monte carlo method and a feed forward neural network. Results show that perturbing the observations provides a good forecasting spread for at least some of the methods. However, for other methods the spread is reduced significantly. Most of the used methods are able to provide good forecastst. However, hyperparameter tuning for the lightGBM boosting algorithm and the neural network is still needed.
Foraminiferal tracers of Indian-Atlantic interocean exchange during the last 600 kyr
Authors: Pérez-Asensio José N. , Tachikawa Kazuyo , de Garidel-Thoron Thibault , Vidal Laurence , Sonzogni Corinne , Guihou Abel , Chen Min-Te
Published: March 2020

The Indian-Atlantic interocean exchange (IAIE), occurring through Agulhas current and its leakage around the southern tip of Africa, is one of the return flows of global thermohaline circulation that contributes to the temperate climate in Europe. The IAIE affects the transport of heat and salt to the zone of deep-water formation in the N Atlantic, influencing the variability of Atlantic Meridional Overturning Circulation (AMOC). During the last 600 kyr, significant climatic events took place such as the Mid-Bruhnes event (MBE) (~430 ka) that marks a transition towards more intense interglacial periods.

The main objective of our study is to assess the impact of climate forcing on the strength of both surface and deep water IAIE during the last 600 kyr. For this purpose, we examined the variability of a group of warm-water planktonic foraminiferal species for tracing surface water circulation. We combined published and unpublished data from 3 cores along an Indian-Atlantic transect: two cores in the Indian Ocean, core MD96-2048 (26°10’S, 34°01’E, 660 m) in the source of the Agulhas current and our study core MD96-2077 (33º10’S, 31º14’E, 3781 m) in the middle of the Agulhas current; and one core in the Atlantic Ocean, core ODP1087 (31°27’S, 15°18’E 1372 m) recording the Agulhas leakage.

Since Globorotalia menardii and Globorotalia tumida are frequently used to trace Agulhas leakage, their variability in Agulhas current in the Indian Ocean is of our interest. Therefore, we compared the relative abundances of the warm-water planktonic G. menardii and G. tumida species with a group of warm-water planktonic foraminiferal species to record the strength of Agulhas current in core MD96-2077. Our results show that the group of warm-water planktonic species reflects increased Agulhas current strength at glacial terminations coinciding with stronger Agulhas leakage (Atlantic core ODP1087) as observed in previous studies. However, in core MD96-2077, both G. menardii and G. tumida relative abundances increase during interglacial periods. This indicates that production of these species in the Agulhas current source region is unlikely to trace Agulhas leakage in the Atlantic Ocean. The analyses of deep-water circulation proxies (Nd isotopes, benthic O and C stable isotopes) are in progress, and they will allow us to assess the response of deep circulation to changes in Agulhas current and leakage over the last 600 kyr.
Influence of tides on the ionospheric annual anomalies
Authors: Ren Zhipeng , Wan Weixing , Xiong Jiangang , Liu Libo , Li Xing
Published: March 2020

Through respectively adding June tides and December tides at the low boundary of GCITEM-IGGCAS model (Global Coupled Ionosphere-Thermosphere-Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate the influence of tides on the annual anomalies of the ionospheric electron density. The tides’ influence on the annual anomalies of the ionospheric electron density varies with latitude, altitude and solar activity level. Compared with the density driven by December tides, the June tides mainly increases the lower ionospheric electron density, and mainly decreases the electron density at higher ionosphere. In the low-latitude ionosphere, tide drives an additional equatorial ionization anomaly structure (EIA) at higher ionosphere in the relative difference of electron density, which suggests that tide affect the equatorial vertical E×B plasma drifts. Although the lower ionospheric annual anomalies driven by tides mainly increases with the increase of solar activity, the annual anomalies at higher ionosphere mainly decreases with solar activity.
MOTEDAS Century database, Part 1: temperature evolution in Spanish Mainland (1916-2015).
Authors: Peña-Angulo Dhais , Sandonís-Pozo Leire , Brunetti Michele , Beguería Santiago , Gonzalez-Hidalgo José Carlos
Published: March 2020

We have finished the complete digitalization of Annual Books from the Spanish meteorological service (AEMET) between 1916 to 1949. Data retrieved included monthly means of maximum and minimum temperature. In the present contribution we are going to show the new MOTEDAS_Century dataset (MOnthly TEmperature Dataset of Spain century) which has been performed matching data from the annual books and data from the national climate data bank of AEMET. The amount of stations with temperature data vary from a minimum of 228 (1938) and 2.030 (1994). This length of the time series is sometimes very short. Since we aim to analyse the information with a highest spatial density as possible we decided, instead of reconstructing series, to reconstruct monthly fields independently by using all the information available month to month between 1916 and 2015. Monthly interpolated data were converted to a high-resolution grid (10x10 km) using the Angular Distance Weighting method, resulting into a 5000 pixels grid.

 

The time series of annual mean temperature in Spanish mainland from 1916 to 2015 shows the well-known pattern of increase during the first decades, a slowdown in the middle of the 20th century, and the final rise since the 1970´s, including a final stage without significant trend for the last three decades.

 

MOTEDAS_Century´s annual temperature average series has been compared with other analogous series from BEST (Berkelay Earth Surface Temperature) and SDAT (Spanish Daily Adjusted Temperature Series) datasets, as well as the twentieth century reanalysis for the Iberian Peninsula. The different versions resemble the global pattern, although differences exist particularly during the last three decades. The comparison of the annual mean temperature series with their counterparts in the BEST, AEMET and SDAT databases suggests that processing the newly retrieved information does not modify the behaviour patterns of mean annual temperatures in the Spanish mainland, and that the difference observed among the various sources can be attributed to a combination of effects from the different number of weather stations examined, which is very much higher in MOTEDAS_century, to the local characteristics of stations. The MOTEDAS_century grid in the anomalies format is available on request from the authors and will be in future on the website of the CLICES Project (http://clices.unizar.es).
Looking high and low: comparing a UAV-based and a ground-based methodology for the detection of vineyard terrace failures
Authors: Pijl Anton , Quarella Edoardo , Vogel Teun A. , D'Agostino Vincenzo , Tarolli Paolo
Published: March 2020

Agricultural terraces are known to be related to complex hillslope hydrology, characterized by surface and sub-surface water flows. Locally high fluxes or accumulation of water can be responsible for terrace wall failures, such as collapse and piping. There is a need for both scientific research and applied sustainable viticulture to better understand these processes. A key challenge is to find a suitable balance between highly integrated but local field measurements, and a more approximate but widespread approach such as remote sensing. In this study, two distinctive methodologies were applied in order to locate and explain terrace wall failure observed in a north-Italian vineyard: a field-based vs. a remote sensing approach. The field-based approach was based on spatially distributed measurements of topsoil soil moisture content using Time Domain Reflectometry (TDR) instrument. This survey revealed high relative soil water concentration at the damaged terraces, in both wet and dry conditions. Furthermore, a unique cross-sectional saturation profile was found above the damaged walls, with the highest values found near the edges. The remote sensing approach was based on a photogrammetric survey and subsequent high-resolution digital terrain analysis and modeling using the Topographic Wetness Index (TWI) and SIMulated Water Erosion model (SIMWE). Results showed how the formation of surface water flow patterns explains the location of damaged walls. These findings show both the opportunities and limitations of the two approaches. Field measurements provided more conclusive information about the location of walls at risk (high predictive potential), but this approach is relatively labour-intensive (low upscaling potential) as compared to a remote sensing approach. The latter can be a powerful tool for acquiring fully distributed estimations of wall failure over larger non-instrumented areas.
Leaf-scale quantification of the effect of photosynthetic gas exchange on Δ17O of atmospheric CO2
Authors: Adnew Getachew , Pons Thijs , Koren Gerbrand , Peters Wouter , Röckmann Thomas
Published: March 2020

 

 

Understanding the processes affecting the triple oxygen isotope composition of atmospheric CO2 during photosynthesis can help to constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions, using sunflower (Helianthus annuus), an annual C3 species with high photosynthetic capacity and stomatal conductance for CO2, an evergreen C3 species, ivy (Hedera hybernica) with lower values for these traits, and a C4 species maize (Zea mays) that has a high photosynthetic capacity and low stomatal conductance. The experiments were conducted at different light intensities and using CO2 with different 17O- excess. Our results demonstrate that two key factors determine the effect of photosynthetic gas exchange on Δ17O of atmospheric CO2: The relative difference in Δ17O of the CO2 entering the leaf and Δ17O of leaf water, and the back-diffusion flux from the leaf to the atmosphere, which can be quantified by the cm/ca ratio.  At low cm/ca the discrimination is governed by diffusion into the leaf, and at high cm/ca by back-diffusion of CO2 that has equilibrated with the leaf water. Plants with a higher cm/ca ratio modify the Δ17O of atmospheric CO2 more strongly than plants with lower cm/ca. 

Based on the leaf cuvette experiments using both C4 and C3 plants, the global discrimination in 17O-excess of atmospheric CO2 due to assimilation is estimated to be -0.6±0.2‰. The main uncertainty in the global estimation is due to the uncertainty in the cm/ca ratio.

 

 

 
Where’s the fire? Using in-situ observations from the NOAA/NASA FIREX-AQ campaign to validate small fire in the central and southern U.S.
Authors: Rintsch Eileen , McCarty Jessica L.
Published: March 2020

Crop residue and rangeland burning is a common practice in the United States but verified ground-based estimates for the frequency of these fires is sparse. We present a comparison between known fire locations collected during the summer 2019 NOAA/NASA FIREX-AQ field campaign with several satellite-based active fire detections to estimate the occurrence of small-scale fires in agroecosystems. Many emissions inventories at the state-, country-, and global-level are driven by active fire detections and not burned area estimates for small fires in agroecosystems. The study area is focused on the southern Great Plains and Mississippi Delta of the United States. We combined fire occurrence data from 375 m Visible Infrared Imaging Spectrometer (VIIRS), 1 km Moderate Resolution Imaging Spectroradiometer (MODIS), and 2 km Geostationary Operational Environmental Satellite (GOES) active fires with 30 m land use data from U.S. Department of Agriculture Cropland Data Layer (CDL). The detections were compared to fires and land use validated in the field during the NOAA/NASA FIREX-AQ mission. GOES detected these fires at a higher frequency than MODIS or VIIRS. For example, MODIS detected 873 active fires and VIIRS detected 2,859, while GOES detected 13,634 active fires. Additionally, a large amount of the fires documented in the field, approximately 41%, were not detected by any satellite instrument used in the study. If GOES detections are excluded, approximately 5% of the documented fires were detected. This suggests that a large amount of cropland and rangeland burning are not detected by current active fire products from polar orbiting satellites like MODIS and VIIRS, with implications for regional air pollution monitoring, emissions inventories, and climate impacts of open burning.  
Creating a global database with return periods of extreme sea levels caused by tropical and extratropical cyclones
Authors: Dullaart Job
Published: March 2020

Storm surges are driven by low air pressure and strong winds in tropical (TC) and extratropical cyclones (ETC). Coastal flooding is often caused by this type of extreme weather with large socio-economic impacts in densely populated and low-lying coastal areas. Recent examples of coastal disasters include typhoon Hagibis that made landfall in Japan, Hurricane Dorian which devastated the northwestern Bahamas, and extratropical cyclone Xaver that affected northern Europe. Each of these storms generated dangerous storm surges, reaching 6m in some parts of the Bahamas during Hurricane Dorian with approximately 100 fatalities as a result. Economic losses are estimated at 10 billion U.S. Dollars for both typhoon Hagibis and hurricane Dorian.

To inform flood risk management and develop effective adaptation strategies it is important to have accurate information on return periods of extreme sea levels. To date, there exists no global database with return periods of extreme sea levels that fully includes TCs. Global databases of extreme sea levels are typically based on historical climate simulations covering multiple decades. While this is sufficient for ETCs, TCs will be underestimated in such databases. This because TCs have generally low probabilities and affect only a small stretch of coastline, compared to ETCs. A climate reanalysis covering multiple decades includes too few TCs to perform an extreme value analysis. To resolve this, previous studies at local scale have used synthetic TC tracks generated by a statistical model to estimate the probabilities of extreme sea levels.

The aim of this research is to develop a global database of extreme sea levels that include both ETCs and TCs. For ETCs, we force the hydrodynamic Global Tide and Surge Model (GTSM) with ERA5 10-meter wind speed and air pressure data to calculate the return periods of extreme sea levels based on the period 1979-2017. Since ERA5 includes all storms, we filter out extreme sea levels caused by TCs. Preliminary results show that GTSM forced with ERA5 atmospheric data performs well for ETCs. For TCs, we force GTSM with synthetic TC tracks that correspond to 10.000 year of TC statistics. The synthetic tracks of TCs are obtained from the STORM model (Bloemendaal et al., in review) based on the International Best Track Archive for Climate Stewardship (IBTrACS) TC database. With STORM it is possible to statistically extend the ~38-year observed dataset to a 10.000-year synthetic dataset. The synthetic dataset preserves the climatological statistics as found in the original dataset. Finally, we will merge the TC and ETC related return periods to create a global extreme sea level database.
Latent Heating Retrieved from TRMM and GPM Satellite Measurements
Authors: Tao Wei-Kuo , Lang Steve , Iguchi Takamichi
Published: March 2020

Latent heat release itself is a consequence of phase changes between the vapor, liquid, and frozen states of water.  This paper will highlight the retrieval of latent heat release from satellite measurements generated by the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Mission (GPM) satellite observatory.  Both TRMM and GPM are providing four-dimensional account of rainfall and its associated precipitation properties over the global Tropics and mid-latitudes: information that can be used to estimate the space-time structure of latent heating.

 

Goddard Convective-Stratiform or CSH retrieved LH is one of two standard LH products (the other one is from Japan Spectral Latent Heating or SLH). This paper will present (1) the new improvements of the CSH LH algorithm by better CRM simulated LH for its look-up table, and (2) the performance of CSH retrieved LH by comparison with surface rainfall rate.  In addition, the similarities and differences of CSH retrieved LH obtained from TRMM and GPM measurements, respectively, will be presented.  At the end of presentation, the further research on latent heating retrieval from satellites will be discussed.
Flexural-isostatic reconstruction of the Western Mediterranean vertical motions after the Messinian Salinity Crisis: implications for sea level and basin connectivity
Authors: Heida Hanneke , Garcia-Castellanos Daniel , Jiménez-Munt Ivone , Raad Fadl , Maillard Agnès , Lofi Johanna
Published: March 2020

The Messinian Salinity Crisis was a period of rapid and extreme environmental change in the Mediterranean occurring from 5.96 to 5.33 Ma, leading to deposition of a huge amount of evaporites in the deep basins and erosion on the margins. Erosional surfaces located deep below current sea level suggest a kilometric drop in sea level commonly associated with the deposition of massive halite deposits during the crisis. However, the timing and magnitude of this sea level drawdown are not well constrained in spite of its important implications for the conditions under which the different MSC sedimentary units were deposited and the connectivity of various sub-basins during the crisis. A 2D (planform) flexural backstripping allows us to restore the Messinian topography in tectonically quiescent areas, constraining the isostatic subsidence due to the (post)Messinian sediment, and the potential effect of falling sea level during the crisis. In this way we restore the elevation of paleoshorelines and the original depth of erosional surfaces and other stratigraphic markers. We apply this method to the area spanning the Valencia Basin, Balearic Promontory and the Algero-Provençal Basin, to restore the Messinian Erosion Surfaces which formed subaerially during the drawdown to their original depth, constraining the minimum base level drop required to erode the margins at these locations. We reconstruct three key moments in the basin history: the pre-crisis basin, the end of halite deposition, and the end of the crisis. We consider multiple scenarios in terms of timing of sea level fall. Preliminary results indicate that over 1 km of sea level drop is required at the end of the Messinian, and over 2 km at the crisis acme to reproduce the observed location of the paleoshorelines, with only small sensitivity to crustal strength. This is in good agreement with estimates from previous backstripping investigations, and provides constraints on the progression of the MSC in the Western Mediterranean.
The contribution of the East Antarctic Ice Sheet to future sea level rise
Authors: Jordan Jim , Gudmundsson Hilmar , Jenkins Adrian , Stokes Chris , Jamieson Stewart , Miles Bertie
Published: March 2020

The East Antarctic Ice Sheet (EAIS) is the single largest potential contributor to future global mean sea level rise, containing a water mass equivalent of 53 m. Recent work has found the overall mass balance of the EAIS to be approximately in equilibrium, albeit with large uncertainties. However, changes in oceanic conditions have the potential to upset this balance. This could happen by both a general warming of the ocean and also by shifts in oceanic conditions allowing warmer water masses to intrude into ice shelf cavities.

We use the Úa numerical ice-flow model, combined with ocean-melt rates parameterized by the PICO box mode, to predict the future contribution to global-mean sea level of the EAIS. Results are shown for the next 100 years under a range of emission scenarios and oceanic conditions on a region by region basis, as well as for the whole of the EAIS. 
Results from An Ensemble Reanalysis with the Community Earth System Model 2.1
Authors: Raeder Kevin , Anderson Jeffrey , Hoar TImothy , Collins Nancy , El Gharamti Moha
Published: March 2020

The National Center for Atmospheric Research (NCAR) has recently released version 2.1 of the Community Earth System Model (CESM 2.1). A twenty-year, 80-member ensemble atmospheric reanalysis with 1-degree resolution in the CAM6 atmospheric model is being produced using NCAR’s Data Assimilation Research Testbed (DART) to support a variety of climate research goals. A standard configuration of CAM and the CLM5 land surface model will be coupled to a prescribed ocean and sea ice. Eventually, the reanalyisis will generate a final product that extends from 1999 to the present. Observations being assimilated include in situ observations used in the operational NCEP CFSR reanalysis along with GPS occultation observations and remote sensing temperature retrievals. The primary goal is to provide an ensemble of atmospheric forcing that can be used to generate additional ensemble reanalyses for other components of CESM including CLM, the POP and MOM6 ocean models, and the CICE sea ice model. Highlights of results from the first 10-years of the reanalysis will be presented. Results will include evaluation of short-term forecasts in observation space for root mean square error, ensemble spread, and ensemble consistency. In addition, key aspects of the atmospheric forcing files for other components of the climate system will be discussed. 
Long-Term Global Ground Heat Flux and Continental Heat Storage from Geothermal Data
Authors: Cuesta-Valero Francisco José , García-García Almudena , Beltrami Hugo , González-Rouco J. Fidel , García-Bustamante Elena
Published: March 2020

Energy exchanges among climate subsystems are of critical importance the climate sensitivity of the Earth's system to greenhouse gases, to quantify the magnitude and evolution of the Earth's energy imbalance, and to project the evolution of future climate. Thus, ascertaining the magnitude and change of the Earth's energy partition within climate subsystems has become urgent in recent years.

Here, we provide new global estimates of changes in ground surface temperature, ground surface heat flux and continental heat storage derived from geothermal data using an expanded database and new techniques. Results reveal markedly higher changes in ground heat flux and heat storage within the continental subsurface than previously reported, with land temperature changes of 1K and continental heat gains of around 12 ZJ during the last part of the 20th century relative to preindustrial times. Half of the heat gain by the continental subsurface since 1960 occurred in the last twenty years.
Tropical cyclone activity prediction on subseasonal time-scales
Authors: Camargo Suzana , Lee Chia-Ying , Vitart Frederic , Sobel Adam , Tippett Michael , Wang Shuguang , Camp Joanne
Published: March 2020

We will first examine the skill of probabilistic tropical cyclone (TC) occurrence and intensity (ACE - accumulated cyclone energy) predictions in the Subseasonal to Seasonal (S2S) dataset. We show that some of the models in the S2S dataset have skill in predicting TC occurrence 4 weeks in advance. In contrast, only one of the models (ECMWF) has skill in predicting the anomaly of TC occurrence from the seasonal climatology beyond week 1. For models with significant mean biases, calibrating the forecast can improve the models’ prediction skill. In contrast, for models with small mean biases, calibration does not guarantee an improvement in model skill as measured by the Brier Skill Score. 

We then focus only on the ECMWF model and using cluster analysis examine the sensitivity of the North Atlantic TC tracks biases to various factors, such as model resolution, lead time, and tracking. We also explore how well the ECMWF North Atlantic TC model tracks in each cluster simulate the known response to climate modes, such as ENSO and MJO. By applying simple bias corrections to each cluster of Atlantic TC tracks, we examine if we can improve the model skill in landfall prediction in the US and Caribbean.
Properties of OH roto-vibrational level populations in the Earth's mesopause region
Authors: Noll Stefan , Winkler Holger , Goussev Oleg , Proxauf Bastian
Published: March 2020

Chemiluminescent OH airglow emission dominates the nighttime radiation of the Earth's atmosphere in the near-infrared wavelength regime. It is an important indicator of the state and variability of the mesopause region at about 90 km. However, the interpretation of the line intensities suffers from uncertainties in the knowledge of the complex roto-vibrational level population distribution, which is far from local thermodynamic equilibrium (LTE). For a better understanding, we investigated these populations in detail mainly based on a high-quality high-resolution mean spectrum from the UVES echelle spectrograph at Cerro Paranal in Chile, which allowed us to measure about 1,000 individual lines including numerous resolved Λ-doublet components between 560 and 1060 nm. As the quality of the currently available sets of OH Einstein-A coefficients is not sufficient for accurate population retrievals, we derived an improved set by a semi-empirical approach, which benefited from the measurement of multiple lines with the same upper level. The resulting populations indicate a clear bimodality for each vibrational level, which is characterised by a cold component indicating the ambient temperature at the OH layer heights and a hot non-LTE component dominating high rotational levels. Our promising two-population fits allowed us to constrain the non-LTE contributions to rotational temperatures based on lines with upper states with low rotational and fixed vibrational quantum number, which are widely used to estimate temperatures in the mesopause region. The bimodality is also clearly indicated by the different population changes depending on the effective altitude of the OH emission layer. Only the cold component significantly decreases with increasing altitude. Our results will be very useful for the challenging modelling of the OH thermalisation process.
A New Model to Describe the Magnetic Structure of CMEs
Authors: Al-Haddad Nada , Lugaz Noé
Published: March 2020

The structure of coronal mass ejections (CMEs) has been the center of numerous studies over the past few decades. Defining the magnetic field orientation locally and globally has proven to be a challenging problem, due to the limited nature of observations that we have, as well as our reliance on the current paradigm of highly-twisted flux ropes. Studies suggest that not all CMEs measured in situ fit within the simple twisted and well-organized flux rope topology. Additionally, many of the events that can be well fitted by existing static flux rope models, do not have as simple a structure as that assumed by the models. This is clear from remote observations and multi-spacecraft measurements. With the wealth of data that we have today, as well as the affluence of research and analysis performed over the last 40 years, it is dues time to present an alternative paradigm, that better represents those data. In this work, we discuss this new paradigm and the literature leading to it. 
Spatio-temporal variability of natural organic matter in Lancang River: concentration, sources and destination
Authors: Wang Ting
Published: March 2020

Natural organic matter (NOM) played an important role in the riverine and global carbon cycle. In order to evaluate the impact of river discharge and anthropogenic activities on the spatio-temporal variability of NOM content and sources in Lancang River, China, a comprehensive study was conducted in two years from the head to the leave-boundary section. As results, the DOC value ranged among 0.91-2.80 mg/L, with sharp decrease in the middle reaches and downstream. While the SOC value significantly enhanced along the water flow, varied from 0.06% to 3.54%. The isotopic composition of organic carbon (δ13C) suggested that predominant contribution of NOM is C3 plants in the upper reach, algae and soil organic matter in the middle reach, and aquatic plants in the downstream. EEM-PARAFAC results proved that NOM in Lancang River is mainly terrestrial organic carbon, while in situ microbial transformed NOM is very low. Moreover, the sharp increase of dissolved CO2 concentration in the lower reaches confirmed the strong respiration of microorganisms due to the higher DO and water temperature, thus resulted in the significantly different fluctuations of DOC and SOC.