Evaluation of Simulated CO_2 Concentrations from the CarbonTracker-Asia Model Using In-situ Observations over East Asia for 2009–2013

The CarbonTracker(CT) model has been used in previous studies for understanding and predicting the sources, sinks, and dynamics that govern the distribution of atmospheric CO_2 at varying ranges of spatial and temporal scales. However, there are still challenges for reproducing accurate model-simulated CO_2 concentrations close to the surface, typically associated with high spatial heterogeneity and land cover. In the present study, we evaluated the performance of nested-grid CT model simulations of CO_2 based on the CT2016 version through comparison with in-situ observations over East Asia covering the period 2009–13. We selected sites located in coastal, remote, inland, and mountain areas. The results are presented at diurnal and seasonal time periods. At target stations, model agreement with in-situ observations was varied in capturing the diurnal cycle. Overall, biases were less than 6.3 ppm on an all-hourly mean basis, and this was further reduced to a maximum of 4.6 ppm when considering only the daytime. For instance, at Anmyeondo, a small bias was obtained in winter, on the order of 0.2 ppm. The model revealed a diurnal amplitude of CO_2 that was nearly flat in winter at Gosan and Anmyeondo stations, while slightly overestimated in the summertime. The model's performance in reproducing the diurnal cycle remains a challenge and requires improvement. The model showed better agreement with the observations in capturing the seasonal variations of CO_2 during daytime at most sites, with a correlation coefficient ranging from 0.70 to 0.99. Also, model biases were within-0.3 and 1.3 ppm, except for inland stations(7.7 ppm).

Specific Relationship between the Surface Air Temperature and the Area of the Terra Nova Bay Polynya,Antarctica

Antarctic polynyas play an important role in regional atmosphere?ice?ocean interactions and are considered to help generate the global deep ocean conveyer belt.Polynyas therefore have a potential impact on the Earth’s climate in terms of the production of sea ice and high-salinity shelf water.In this study,we investigated the relationship between the area of the Terra Nova Bay polynya and the air temperature as well as the eastward and northward wind based on the ERA5 and ERAInterim reanalysis datasets and observations from automatic weather stations during the polar night.We examined the correlation between each factor and the polynya area under different temperature conditions.Previous studies have focused more on the effect of winds on the polynya,but the relationship between air temperature and the polynya area has not been fully investigated.Our study shows,eliminating the influence of winds,lower air temperature has a stronger positive correlation with the polynya area.The results show that the relationship between the polynya area and air temperature is more likely to be interactively influenced.As temperature drops,the relationship of the polynya area with air temperature becomes closer with increasing correlation coefficients.In the low temperature conditions,the correlation coefficients of the polynya area with air temperature are above 0.5,larger than that with the wind speed.

Verification and Correction of Cloud Base and Top Height Retrievals from Ka–band Cloud Radar in Boseong,Korea

In this study,cloud base height（CBH） and cloud top height（CTH） observed by the Ka-band（33.44 GHz） cloud radar at the Boseong National Center for Intensive Observation of Severe Weather during fall 2013（September-November） were verified and corrected.For comparative verification,CBH and CTH were obtained using a ceilometer（CL51） and the Communication,Ocean and Meteorological Satellite（COMS）.During rainfall,the CBH and CTH observed by the cloud radar were lower than observed by the ceilometer and COMS because of signal attenuation due to raindrops,and this difference increased with rainfall intensity.During dry periods,however,the CBH and CTH observed by the cloud radar,ceilometer,and COMS were similar.Thin and low-density clouds were observed more effectively by the cloud radar compared with the ceilometer and COMS.In cases of rainfall or missing cloud radar data,the ceilometer and COMS data were proven effective in correcting or compensating the cloud radar data.These corrected cloud data were used to classify cloud types,which revealed that low clouds occurred most frequently.

Global Response to Tropical Diabatic Heating Variability in Boreal Winter

Global teleconnections associated with tropical convective activities were investigated, based on monthly data of 29 Northern Hemisphere winters： December, January, February, and March （DJFM）. First, EOF analyses were performed on the outgoing longwave radiation （OLR） data to characterize the convective ac tivity variability in the tropical Indian Ocean and the western Pacific. The first EOF mode of the convective activity was highly correlated with the ENSO. The second EOF mode had an east–west dipole structure, and the third EOF mode had three convective activity centers. Two distinct teleconnection patterns were identified that were associated, respectively, with the second and third EOF modes. A global primitive equation model was used to investigate the physical mechanism that causes the global circulation anoma lies. The model responses to anomalous tropical thermal forcings that mimic the EOF patterns matched the general features of the observed circulation anomalies well, and they were mainly controlled by linear processes. The importance of convective activities in the tropical Indian Ocean and western Pacific to the extended and longrange forecasting capability in the extratropics is discussed.

A Precipitation Detection Method for MWTS-Ⅱ Radiance Assimilation in Typhoon Simulation

FY-3C Microwave Temperature SounderⅡ(MWTS-Ⅱ)lacks observations at 23.8 GHz,31 GHz and 89 GHz,making it difficult to remove the data contaminated by precipitation in assimilation.In this paper,a fast forward operator based on the Community Radiative Transfer Model(CRTM)was used to analyze the relationship between the observation minus background simulation(O-B)and the cloud fractions in different MWTS-Ⅱchannels.In addition,based on the community Gridpoint Statistical Interpolation(GSI)system,the radiation brightness temperature of the MWTS-Ⅱwas assimilated in the regional Numerical Weather Prediction(NWP)model.In the process of assimilation,Visible and Infrared Radiometer(VIRR)cloud detection products were matched to MWTS-Ⅱpixels for precipitation detection.For typhoon No.18 in 2014,impact tests of MWTS-Ⅱdata assimilation was carried out.The results show that,though the bias observation minus analysis(O-A)of assimilated data can be reduced by quality control only with|O-B|<3 K;however,the O-A becomes much smaller while the precipitation detection is performed with Fvirr<0.9(VIRR cloud fraction threshold of 0.9).Besides,the change of the environmental field around the typhoon is more conducive to make the simulated track closer to the observation.The 72-hour typhoon track simulation error also shows that,after the precipitation detection,the error of simulated typhoon track is significantly reduced,which reflects the validity of a precipitation detection method based on a double criterion of|O-B|<3 K and Fvirr<0.9.

Land Response to Atmosphere at Different Resolutions in the Common Land Model over East Asia

Towards a better understanding of hydrological interactions between the land surface and atmosphere, land surface mod- els are routinely used to simulate hydro-meteorological fluxes. However, there is a lack of observations available for model forcing, to estimate the hydro-meteorological fluxes in East Asia. In this study, Common Land Model （CLM） was used in offline-mode during the summer monsoon period of 2006 in East Asia, with different forcings from Asiaflux, Korea Land Data Assimilation System （KLDAS）, and Global Land Data Assimilation System （GLDAS）, at point and regional scales, separately. The CLM results were compared with observations from Asiaflux sites. The estimated net radiation showed good agreement, with r = 0.99 for the point scale and 0.85 for the regional scale. The estimated sensible and latent heat fluxes using Asiaflux and KLDAS data indicated reasonable agreement, with r = 0.70. The estimated soil moisture and soil temperature showed similar patterns to observations, although the estimated water fluxes using KLDAS showed larger discrepancies than those of Asiaflux because of scale mismatch. The spatial distribution of hydro-meteorological fluxes according to KLDAS for East Asia were compared to the CLM results with GLDAS, and the GLDAS provided online. The spatial distributions of CLM with KLDAS were analogous to CLM with GLDAS, and the standalone GLDAS data. The results indicate that KLDAS is a good potential source of high spatial resolution forcing data. Therefore, the KLDAS is a promising alternative product, capable of compensating for the lack of observations and low resolution grid data for East Asia.

On the Dynamical Analysis in Aftershock Networks

We investigate the dynamical behavior of aftershocks in earthquake networks, and the earthquake network calculated from a time series is constructed by contemplating cell resolution and temporal causality. We attempt to connect an earthquake network using relationship between one main earthquake and its aftershocks from seismic data of California. We mainly examine some topological properties of the earthquake such as the degree distribution, the characteristic path length, the clustering coefficient, and the global efficiency. Our result cannot presently determine the universal scaling exponents in statistical quantities, but the topological properties may be inferred to advance and improve by implementing the method and its technique of networks. Particularly, it may be dealt with a network issue of convenience and of importance in the case how large networks construct in time to proceed on earthquake systems.