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- Prediction of Seasonal Tropical Cyclone Activity in the NUIST-CFS1.0
Forecast System-
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Abstract: Prediction skill for the seasonal tropical cyclone (TC) activity in the Northern Hemisphere is investigated using the coupled climate forecast system (version 1.0) of Nanjing University of Information Science and Technology (NUIST-CFS1.0). This assessment is based on the seven-month (May to November) hindcasts consisting of nine ensemble members during 1982–2019. The predictions are compared with the Japanese 55-year Reanalysis and observed tropical storms in the Northern Hemisphere. The results show that the overall distributions of the TC genesis and track densities in model hindcasts agree well with the observations, although the seasonal mean TC frequency and accumulated cyclone energy (ACE) are underestimated in all basins due to the low resolution (T106) of the atmospheric component in the model. NUIST-CFS1.0 closely predicts the interannual variations of TC frequency and ACE in the North Atlantic (NA) and eastern North Pacific (ENP), which have a good relationship with indexes based on the sea surface temperature. In the western North Pacific (WNP), NUIST-CFS1.0 can closely capture ACE, which is significantly correlated with the El Niño—Southern Oscillation (ENSO), while it has difficulty forecasting the interannual variation of TC frequency in this area. When the WNP is further divided into eastern and western subregions, the model displays improved TC activity forecasting ability. Additionally, it is found that biases in predicted TC genesis locations lead to inaccurately represented TC—environment relationships, which may affect the capability of the model in reproducing the interannual variations of TC activity.
PubDate: 2023-07-01
- Homogenised Monthly and Daily Temperature and Precipitation Time Series in
China and Greece since 1960-
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Abstract: In this paper, we describe and analyze two datasets entitled “Homogenised monthly and daily temperature and precipitation time series in China during 1960–2021” and “Homogenised monthly and daily temperature and precipitation time series in Greece during 1960–2010”. These datasets provide the homogenised monthly and daily mean (TG), minimum (TN), and maximum (TX) temperature and precipitation (RR) records since 1960 at 366 stations in China and 56 stations in Greece. The datasets are available at the Science Data Bank repository and can be downloaded from https://doi.org/10.57760/sciencedb.01731 and https://doi.org/10.57760/sciencedb.01720. For China, the regional mean annual TG, TX, TN, and RR series during 1960–2021 showed significant warming or increasing trends of 0.27°C (10 yr)−1, 0.22°C (10 yr)−1, 0.35°C (10 yr)−1, and 6.81 mm (10 yr)−1, respectively. Most of the seasonal series revealed trends significant at the 0.05 level, except for the spring, summer, and autumn RR series. For Greece, there were increasing trends of 0.09°C (10 yr)−1, 0.08°C (10 yr)−1, and 0.11°C (10 yr)−1 for the annual TG, TX, and TN series, respectively, while a decreasing trend of −23.35 mm (10 yr)−1 was present for RR. The seasonal trends showed a significant warming rate for summer, but no significant changes were noted for spring (except for TN), autumn, and winter. For RR, only the winter time series displayed a statistically significant and robust trend [−15.82 mm (10 yr)−1]. The final homogenised temperature and precipitation time series for both China and Greece provide a better representation of the large-scale pattern of climate change over the past decades and provide a quality information source for climatological analyses.
PubDate: 2023-07-01
- Characteristics of PM2.5 and Its Reactive Oxygen Species in Heating Energy
Transition and Estimation of Its Impact on the Environment and Health in
China—A Case Study in the Fenwei Plain-
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Abstract: To reduce the adverse effects of traditional domestic solid fuel, the central government began implementing a clean heating policy in northern China in 2017. Clean coal is an alternative low-cost fuel for rural households at the present stage. In this study, 18 households that used lump coal, biomass, and clean coal as the main fuel were selected to evaluate the benefits of clean heating transformation in Tongchuan, an energy city in the Fenwei Plain, China. Both indoor and personal exposure (PE) samples of fine particulate matter (PM2.5) were synchronically collected. Compared with the lump coal and biomass groups, the indoor PM2.5 concentration in the clean coal group is 43.6% and 20.0% lower, respectively, while the values are 16.8% and 21.3% lower, respectively, in the personal exposure samples. PM2.5-bound elements Cd, Ni, Zn, and Mn strongly correlated with reactive oxygen species (ROS) levels in all fuel groups, indicating that transition metals are the principal components to generate oxidative stress. Using a reliable estimation method, it is predicted that after the substitution of clean coal as a household fuel, the all-cause, cardiovascular, and respiratory disease that causes female deaths per year could be reduced by 16, 6, and 3, respectively, in the lump coal group, and 22, 8, and 3, respectively, in the biomass group. Even though the promotion of clean coal has led to impressive environmental and health benefits, the efficiencies are still limited. More environmental-friendly energy sources must be promoted in the rural regions of China.
PubDate: 2023-07-01
- Black Carbon Size in Snow of Chinese Altai Mountain in Central Asia
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Abstract: Black carbon (BC) in snow plays an important role to accelerate snow melting. However, current studies mostly focused on BC concentrations, few on their size distributions in snow which affected BC’s effect on albedo changes. Here we presented refractory BC (rBC) concentrations and size distributions in snow collected from Chinese Altai Mountains in Central Asia from November 2016 to April 2017. The results revealed that the average rBC concentrations were 5.77 and 2.82 ng g−1 for the surface snow and sub-surface snow, which were relatively higher in the melting season (April) than that in winter (November–January). The mass median volume-equivalent diameter of rBC size in surface snow was approximately at 120–150 nm, which was typically smaller than that in the atmosphere (about 200 nm for urban atmosphere). However, there existed no specific mass median volume-equivalent diameter of BC size for sub-surface snow in winter. While during the melting season, the median mass size of rBC in sub-surface snow was similar to that in surface snow. Backward trajectories indicated that anthropogenic sourced BC dominated rBC in snow (70%–85%). This study will promote our understanding on BC size distributions in snow, and highlight the possible impact of BC size on climate effect.
PubDate: 2023-07-01
- An Interdecadal Change in the Influence of the NAO on Atlantic-Induced
Arctic Daily Warming around the Mid-1980s-
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Abstract: After approaching 0°C owing to an Atlantic storm at the end of 2015, the Arctic temperature approached freezing again in 2022, indicating that Arctic daily warming events remain a concern. The NCEP/NCAR Reanalysis dataset was used to investigate the influence of the NAO on the Arctic winter daily warming events induced by Atlantic storms, known as the Atlantic pattern-Arctic Rapid Tropospheric Daily Warming (Atlantic-RTDW) event. Atlantic-RTDW events are triggered by Atlantic storms that transport warm and humid air masses moving into the Arctic. Furthermore, an interdecadal change in the influence of NAO on Atlantic-RTDW-event frequency was observed around the mid-1980s. Specifically, before the mid-1980s (pre-transition period), 500-hPa southerly (northerly) wind anomalies occupied the North Atlantic (NA) in the positive (negative) phase of NAO, which increased (decreased) the Atlantic-RTDW events occurrence by steering Atlantic storms into (away from) the Arctic; thus, the NAO could potentially influence the Atlantic-RTDW-event frequency. However, the relationship between the NAO and the Atlantic-RTDW-event frequency has weakened since the mid-1980s (post-transition period). In the post-transition period, such 500-hPa southerly (northerly) wind anomalies over the NA hardly existed in the positive (negative) phase of NAO, which was attributed to a stronger Atlantic Storm Track (AST) activity intensity than that in the pre-transition period. During this period, the strong AST induced an enhanced NAO-related cyclone via transient eddy-mean flow interactions, resulting in the disappearance of southerly and northerly wind anomalies over the NA.
PubDate: 2023-07-01
- Asymmetry of Salinity Variability in the Tropical Pacific during
Interdecadal Pacific Oscillation Phases-
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Abstract: It has been recognized that salinity variability in the tropical Pacific is closely related to the Interdecadal Pacific Oscillation (IPO). Here, we use model simulations from 1900 to 2017 to illustrate obvious asymmetries of salinity variability in the tropical Pacific during positive and negative IPO phases. The amplitude of salinity variability in the tropical Pacific during positive IPO phases is larger than that during negative IPO phases, with a more westward shift of a large Sea Surface Salinity (SSS) anomaly along the equator. Salinity budget analyses show that the asymmetry of salinity variability during positive and negative IPO phases is dominated by the difference in the surface forcing associated with the freshwater flux [FWF, precipitation (P) minus evaporation (E)], with a contribution of 40%–50% near the dateline on the equator. Moreover, the relationships between the salinity variability and its budget terms also show differences in their lead-lag correlations during positive and negative IPO phases. These differences in salinity variability during different IPO phases produce asymmetric effects on seawater density which can reduce or enhance upper-ocean stratification. Therefore, the salinity effects may modulate the intensity of El Niño-Southern Oscillation (ENSO), resulting in an enhanced (reduced) El Niño but a reduced (enhanced) La Niña during positive (negative) IPO phases by 1.6°C psu−1 (1.3°C psu−1), respectively. It is suggested that the asymmetry of salinity variability may be related to the recent change in ENSO amplitude associated with the IPO, which can help elucidate ENSO diversity.
PubDate: 2023-07-01
- Evaluation of the Long-term Performance of Microwave Radiation Imager
Onboard Chinese Fengyun Satellites-
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Abstract: Accurate brightness temperature (BT) is a top priority for retrievals of atmospheric and surface parameters. Microwave Radiation Imagers (MWRIs) on Chinese Fengyun-3 (FY-3) serial polar-orbiting satellites have been providing abundant BT data since 2008. Much work has been done to evaluate short-term MWRI observations, but the long-term performance of MWRIs remains unclear. In this study, operational MWRI BTs from 2012–19 were carefully examined by using simultaneous Advanced Microwave Scanning Radiometer 2 (AMSR2) BTs as the reference. The BT difference between MWRI/FY3B and AMSR2 during 2012–19 increased gradually over time. As compared with MWRI/FY3B BTs over land, those of MWRI/FY3D were much closer to those of AMSR2. The ascending and descending orbit difference for MWRI/FY3D is also much smaller than that for MWRI/FY3B. These results suggested the improvement of MWRI/FY3D over MWRI/FY3B. A substantial BT difference between AMSR2 and MWRI was found over water, especially at the vertical polarization channels. A similar BT difference was found over polar water based on the simultaneous conical overpassing (SCO) method. Radiative transfer model simulations suggested that the substantial BT differences at the vertical polarization channels of MWRI and AMSR2 over water were partly contributed by their difference in the incident angle; however, the underestimation of the operational MWRI BT over water remained a very important issue. Preliminary assessment of the operational and recalibrated MWRI BT demonstrated that MWRI BTs were substantially improved after the recalibration, including the obvious underestimation of the operational MWRI BT at the vertical polarization channels over water was corrected, and the time-dependent biases were reduced.
PubDate: 2023-07-01
- Impact of Revised Trigger and Closure of the Double-Plume Convective
Parameterization on Precipitation Simulations over East Asia-
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Abstract: A double-plume convective parameterization scheme is revised to improve the precipitation simulation of a global model (Global-to-Regional Integrated Forecast System; GRIST). The improvement is achieved by considering the effects of large-scale dynamic processes on the trigger of deep convection. The closure, based on dynamic CAPE, is improved accordingly to allow other processes to consume CAPE under the more restricted convective trigger condition. The revised convective parameterization is evaluated with a variable-resolution model setup (110−35 km, refined over East Asia). The Atmospheric Model Intercomparison Project (AMIP) simulations demonstrate that the revised convective parameterization substantially delays the daytime precipitation peaks over most land areas, leading to an improved simulated diurnal cycle, evidenced by delayed and less frequent afternoon precipitation. Meanwhile, changes to the threshold of the trigger function yield a small impact on the diurnal amplitude of precipitation because of the consistent setting of dCAPE-based trigger and closure. The simulated mean precipitation remains reasonable, with some improvements evident along the southern slopes of the Tibetan Plateau. The revised scheme increases convective precipitation at the lower levels of the windward slope and reduces the large-scale precipitation over the upper slope, ultimately shifting the rainfall peak southward, which is in better agreement with the observations.
PubDate: 2023-07-01
- Fluorescence Properties and Chemical Composition of Fine Particles in the
Background Atmosphere of North China-
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Abstract: To understand the aerosol characteristics in a regional background environment, fine-particle (PM2.5, n = 228) samples were collected over a one-year period at the Shangdianzi (SDZ) station, which is a Global Atmospheric Watch regional background station in North China. The chemical and optical characteristics of PM2.5 were analyzed, including organic carbon, elemental carbon, water-soluble organic carbon, water-soluble inorganic ions, and fluorescent components of water-soluble organic matter. The source factors of major aerosol components are apportioned, and the sources of the fluorescent chromophores are further analyzed. The major chemical components of PM2.5 at SDZ were NO3−, organic matter, SO42−, and NH4+. Annually, water-soluble organic carbon contributed 48% ± 15% to the total organic carbon. Secondary formation (52%) and fossil fuel combustion (63%) are the largest sources of water-soluble organic matter and water-insoluble organic matter, respectively. In addition, three humic-like and one protein-like matter were identified via parallel factor analysis for excitation—emission matrices. The fluorescence intensities of the components were highest in winter and lowest in summer, indicating the main impact of burning sources. This study contributes to understanding the chemical and optical characteristics of ambient aerosols in the background atmosphere.
PubDate: 2023-07-01
- Phosphorus Limitation on Carbon Sequestration in China under RCP8.5
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Abstract: Currently, there is a lack of understanding regarding carbon (C) sequestration in China arising as a result of phosphorus (P) limitation. In this study, a global land surface model (CABLE) was used to investigate the response of C uptake to P limitation after 1901. In China, P limitation resulted in reduced net primary production (NPP), heterotrophic respiration, and net ecosystem production (NEP) in both the 2030s and the 2060s. The reductions in NEP in the period 2061–70 varied from 0.32 Pg C yr−1 in China to 5.50 Pg C yr−1 at the global scale, translating to a decrease of 15.0% for China and 7.6% globally in the period 2061–70, relative to the changes including C and nitrogen cycles. These ranges reflect variations in the magnitude of P limitation on C uptake (or storage) at the regional and global scales. Both in China and at the global scale, these differences can be attributed to differences in soil nutrient controls on C uptake, or positive feedback between NPP and soil decomposition rates, or both. Our results highlight the strong ability of P limitation to influence the pattern, response, and magnitude of C uptake under future conditions (2030s–2060s), which may help to clarify the potential influence of P limitation when projecting C uptake in China.
PubDate: 2023-07-01
- Seasonal Prediction of Extreme High-Temperature Days in Southwestern China
Based on the Physical Precursors-
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Abstract: Extreme high temperatures frequently occur in southwestern China, significantly impacting the local ecological system and economic development. However, accurate prediction of extreme high-temperature days (EHDs) in this region is still an unresolved challenge. Based on the spatiotemporal characteristics of EHDs over China, a domain-averaged EHD index over southwestern China (SWC-EHDs) during April–May is defined. The simultaneous dynamic and thermodynamic fields associated with the increased SWC-EHDs are a local upper-level anticyclonic (high-pressure) anomaly and wavy geopotential height anomaly patterns over Eurasia. In tracing the origins of the lower boundary anomalies, two physically meaningful precursors are detected for SWC-EHDs. They are the tripolar SST change tendency from December–January to February–March in the northern Atlantic and the February–March mean snow depth in central Asia. Using these two selected predictors, a physics-based empirical model prediction was applied to the training period of 1961–2005 to obtain a skillful prediction of the EHDs index, attaining a correlation coefficient of 0.76 in the independent prediction period (2006–19), suggesting that 58% of the total SWC-EHDs variability is predictable. This study provides an estimate for the lower bound of the seasonal predictability of EHDs as well as for the hydrological drought over southwestern China.
PubDate: 2023-07-01
- Interannual Meridional Displacement of the Upper-Tropospheric Westerly Jet
over Western East Asia in Summer-
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Abstract: The interannual meridional displacement of the upper-tropospheric westerly jet over the eastern portion of East Asia in summer has been well documented. This study, however, investigates the interannual meridional displacement of the westerly jet over the western portion of East Asia in summer, which is distinct from its eastern counterpart. The results show that the meridional displacement of the western East Asian jet shows a clear asymmetric feature; that is, there are remarkable differences between the southward and northward displacement of the jet. The southward displacement of the jet corresponds to suppressed convection in the tropical western North Pacific and Maritime Continent and enhanced convection in the equatorial Pacific, which can be explained by the warmer sea surfaces found in the northern Indian Ocean and equatorial eastern Pacific. These tropical anomalies somewhat resemble those associated with the eastern East Asian jet variability. However, the northward displacement of the western East Asian jet does not correspond to significant convection and SST anomalies in the entire tropics; instead, the northward displacement of the jet corresponds well to the positive phase of the Arctic Oscillation. Furthermore, the meridional displacement of the western jet has asymmetric impacts on rainfall and surface air temperatures in East Asia. When the western jet shifts northward, more precipitation is found over South China and Northeast China, and higher temperatures appear in northern China. By contrast, when the jet shifts southward, more precipitation appears over the East Asian rainy belt, including the Yangtze River valley, South Korea, and southern and central Japan and warmer temperatures are found South and Southeast Asia.
PubDate: 2023-07-01
- Raindrop Size Distribution Measurements at High Altitudes in the
Northeastern Tibetan Plateau during Summer-
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Abstract: Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau. The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m. The results show that the contribution of stratiform and convective precipitation with rain rate between 1 ⩽R<5 mm h−1 to the total precipitation increases with altitude, and the raindrop scale and number concentration of convective precipitation is larger than that for stratiform precipitation. The droplet size spectra of both stratiform and convective precipitation shows a single peak with a peak particle size between 0.31–0.50 mm, and they have essentially the same peak particle size and number concentration at the same altitude. The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm, while those of convective clouds range from 4 mm to 8 mm. The Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution. The stratiform precipitation particles are smaller with higher number concentration, while the opposite is true for the convective precipitation particles. The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm, and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period. Moreover, conventional radar estimation methods would underestimate the precipitation in the Northeastern Tibetan Plateau.
PubDate: 2023-07-01
- Monsoon Break over the South China Sea during Summer: Statistical Features
and Associated Atmospheric Anomalies-
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Abstract: This study identifies break events of the South China Sea (SCS) summer monsoon (SCSSM) based on 42 years of data from 1979 to 2020, and investigates their statistical characteristics and associated atmospheric anomalies. A total of 214 break events are identified by examining the convection evolution during each monsoon season. It is found that most events occur between June and September and show a roughly even distribution. Short-lived events (3–7 days) are more frequent, accounting for about two thirds of total events, with the residual one third for long-lived events (8–24 days). The SCSSM break is featured by drastic variations in various atmospheric variables. Particularly, the convection and precipitation change from anomalous enhancement in adjoining periods to a substantial suppression during the break, with the differences being more than 60 W m−2 for outgoing longwave radiation (OLR) and 10 mm d−1 for precipitation. This convection/precipitation suppression is accompanied by an anomalous anticyclone in the lower troposphere, corresponding to a remarkable westward retreat of the monsoon trough from the Philippine Sea to the Indochina Peninsula, which reduces the transportation of water vapor into the SCS. Besides, the pseudo-equivalent potential temperature (θse) declines sharply, mainly attributable to the local specific humidity reduction caused by downward dry advection. Furthermore, it is found that the suppressed convection and anomalous anticyclone responsible for the monsoon break form near the equatorial western Pacific and then propagate northwestward to the SCS.
PubDate: 2023-06-06
- The 17th Workshop on Antarctic Meteorology and Climate and 7th Year of
Polar Prediction in the Southern Hemisphere Meeting-
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PubDate: 2023-06-06
- Evaluation of the Predicted Particle Properties (P3) Microphysics Scheme
in Simulations of Stratiform Clouds with Embedded Convection-
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Abstract: To evaluate the ability of the Predicted Particle Properties (P3) scheme in the Weather Research and Forecasting (WRF) model, we simulated a stratiform rainfall event over northern China on 22 May 2017. WRF simulations with two P3 versions, P3-nc and P3-2ice, were evaluated against rain gauge, radar, and aircraft observations. A series of sensitivity experiments were conducted with different collection efficiencies between ice and cloud droplets. The comparison of the precipitation evolution between P3-nc and P3-2ice suggested that both P3 versions overpredicted surface precipitation along the Taihang Mountains but underpredicted precipitation in the localized region on the leeward side. P3-2ice had slightly lower peak precipitation rates and smaller total precipitation amounts than P3-nc, which were closer to the observations. P3-2ice also more realistically reproduced the overall reflectivity structures than P3-nc. A comparison of ice concentrations with observations indicated that P3-nc underestimated aggregation, whereas P3-2ice produced more active aggregation from the self-collection of ice and ice-ice collisions between categories. Efficient aggregation in P3-2ice resulted in lower ice concentrations at heights between 4 and 6 km, which was closer to the observations. In this case, the total precipitation and precipitation pattern were not sensitive to riming. Riming was important in reproducing the location and strength of the embedded convective region through its impact on ice mass flux above the melting level.
PubDate: 2023-06-06
- Extreme Cold Events in North America and Eurasia in November-December
2022: A Potential Vorticity Gradient Perspective-
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Abstract: From 17 November to 27 December 2022, extremely cold snowstorms frequently swept across North America and Eurasia. Diagnostic analysis reveals that these extreme cold events were closely related to the establishment of blocking circulations. Alaska Blocking (AB) and subsequent Ural Blocking (UB) episodes are linked to the phase transition of the North Atlantic Oscillation (NAO) and represent the main atmospheric regimes in the Northern Hemisphere. The downstream dispersion and propagation of Rossby wave packets from Alaska to East Asia provide a large-scale connection between AB and UB episodes. Based on the nonlinear multi-scale interaction (NMI) model, we found that the meridional potential vorticity gradient (PVy) in November and December of 2022 was anomalously weak in the mid-high latitudes from North America to Eurasia and provided a favorable background for the prolonged maintenance of UB and AB events and the generation of associated severe extreme snowstorms. However, the difference in the UB in terms of its persistence, location, and strength between November and December is related to the positive (negative) NAO in November (December). During the La Niña winter of 2022, the UB and AB events are related to the downward propagation of stratospheric anomalies, in addition to contributions by La Niña and low Arctic sea ice concentrations as they pertain to reducing PVy in mid-latitudes.
PubDate: 2023-06-01
- The Climate Response to Global Forest Area Changes under Different Warming
Scenarios in China-
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Abstract: Human activities have notably affected the Earth’s climate through greenhouse gases (GHG), aerosol, and land use/land cover change (LULCC). To investigate the impact of forest changes on regional climate under different shared socioeconomic pathways (SSPs), changes in surface air temperature and precipitation over China under low and medium/high radiative forcing scenarios from 2021 to 2099 are analyzed using multimodel climate simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Results show that the climate responses to forest changes are more significant under the low radiative forcing scenario. Deforestation would increase the mean, interannual variability, and the trend of surface air temperature under the low radiative forcing scenario, but it would decrease those indices under the medium/high radiative forcing scenario. The changes in temperature show significant spatial heterogeneity. For precipitation, under the low radiative forcing scenario, deforestation would lead to a significant increase in northern China and a significant decrease in southern China, and the effects are persistent in the near term (2021–40), middle term (2041–70), and long term (2071–99). In contrast, under the medium/high radiative forcing scenario, precipitation increases in the near term and long term over most parts of China, but it decreases in the middle term, especially in southern, northern, and northeast China. The magnitude of precipitation response to deforestation remains comparatively small.
PubDate: 2023-06-01
- Radar Quantitative Precipitation Estimation Based on the Gated Recurrent
Unit Neural Network and Echo-Top Data-
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Abstract: The Gated Recurrent Unit (GRU) neural network has great potential in estimating and predicting a variable. In addition to radar reflectivity (Z), radar echo-top height (ET) is also a good indicator of rainfall rate (R). In this study, we propose a new method, GRU_Z-ET, by introducing Z and ET as two independent variables into the GRU neural network to conduct the quantitative single-polarization radar precipitation estimation. The performance of GRU_Z-ET is compared with that of the other three methods in three heavy rainfall cases in China during 2018, namely, the traditional Z-R relationship (Z=300R1.4), the optimal Z-R relationship (Z=79R1.68) and the GRU neural network with only Z as the independent input variable (GRU_Z). The results indicate that the GRU_Z-ET performs the best, while the traditional Z-R relationship performs the worst. The performances of the rest two methods are similar. To further evaluate the performance of the GRU_Z-ET, 200 rainfall events with 21882 total samples during May–July of 2018 are used for statistical analysis. Results demonstrate that the spatial correlation coefficients, threat scores and probability of detection between the observed and estimated precipitation are the largest for the GRU_Z-ET and the smallest for the traditional Z-R relationship, and the root mean square error is just the opposite. In addition, these statistics of GRU_Z are similar to those of optimal Z-R relationship. Thus, it can be concluded that the performance of the GRU_Z-ET is the best in the four methods for the quantitative precipitation estimation.
PubDate: 2023-06-01
- The Subsurface and Surface Indian Ocean Dipoles and Their Association with
ENSO in CMIP6 models-
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Abstract: This study assesses the reproducibility of 31 historical simulations from 1850 to 2014 in the Coupled Model Intercomparison Project phase 6 (CMIP6) for the subsurface (Sub-IOD) and surface Indian Ocean Dipole (IOD) and their association with El Niño-Southern Oscillation (ENSO). Most CMIP6 models can reproduce the leading east-west dipole oscillation mode of heat content anomalies in the tropical Indian Ocean (TIO) but largely overestimate the amplitude and the dominant period of the Sub-IOD. Associated with the much steeper west-to-east thermocline tilt of the TIO, the vertical coupling between the Sub-IOD and IOD is overly strong in most CMIP6 models compared to that in the Ocean Reanalysis System 4 (ORAS4). Related to this, most models also show a much tighter association of Sub-IOD and IOD events with the canonical ENSO than observations. This explains the more (less) regular Sub-IOD and IOD events in autumn in those models with stronger (weaker) surface-subsurface coupling in TIO. Though all model simulations feature a consistently low bias regarding the percentage of the winter-spring Sub-IOD events co-occurring with a Central Pacific (CP) ENSO, the linkage between a westward-centered CP-ENSO and the Sub-IOD that occurs in winter-spring, independent of the IOD, is well reproduced.
PubDate: 2023-06-01
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