Detection of vegetation drying signals using diurnal variation of land surface temperature: Application to the 2018 East Asia heatwave

Satellite-based vegetation monitoring provides important insights regarding spatiotemporal variations in vegetation growth from a regional to continental scale. Most current vegetation monitoring methodologies rely on spectral vegetation indices (VIs) observed by polar-orbiting satellites, which provide one or a few observations per day. This study proposes a new methodology based on diurnal changes in land surface temperatures (LSTs) using Japan's geostationary satellite, Himawari-8/Advanced Himawari Imager (AHI). AHI thermal infrared observation provides LSTs at 10-min frequencies and ∼ 2 km spatial resolution. The DTC parameters that summarize the diurnal cycle waveform were obtained by fitting a diurnal temperature cycle (DTC) model to the time-series LST information for each day. To clarify the applicability of DTC parameters in detecting vegetation drying under humid climates, DTC parameters from in situ LSTs observed at vegetation sites, as well as those from Himawari-8 LSTs, were evaluated for East Asia. Utilizing the record-breaking heat wave that occurred in East Asia in 2018 as a case study, the anomalies of DTC parameters from the Himawari-8 LSTs were compared with the drying signals indicated by VIs, latent heat fluxes (LE), and surface soil moisture (SM). The results of site-based and satellite-based analyses revealed that DTR (diurnal temperature range) correlates with the evaporative fraction (EF) and SM, whereas Tmax (daily maximum LST) correlates with LE and VIs. Regarding other temperature-related parameters, T0 (LST around sunrise), Ta (temperature rise during daytime), and δT (temperature fall during nighttime) are unstable in quantification by DTC model. Moreover, time-related parameters, such as tm (time reaching Tmax), are more sensitive to topographic slope and geometric conditions than surface thermal properties at humid sites in East Asia, although they correlate with EF and SM at a semi-arid site in Australia. Additionally, the spatial distribution of the DTR anomaly during the 2018 heat wave corresponds with the drying signals indicated as negative SM anomalies. Regions with large positive anomalies in Tmax and DTR correspond to area with visible damage to vegetation, as indicated by negative VI anomalies. Hence, combined Tmax and DTR potentially detects vegetation drying indetectable by VIs, thereby providing earlier and more detailed vegetation monitoring in both humid and semi-arid climates

GLOBE: Science and Education

This article provides a brief overview of the GLOBE Program and describes its benefits to scientists, teachers, and students. The program itself is designed to use environmental research as a means to improve student achievement in basic science, mathematics, geography, and use of technology. Linking of students and scientists as collaborators is seen as a fundamental part of the process. GLOBE trains teachers to teach students how to take measurements of environmental parameters at quality levels acceptable for scientific research. Teacher training emphasizes a hands-on, inquiry-based methodology. Student-collected GLOBE data are universally accessible through the Web. An annual review over the past six years indicates that GLOBE has had a positive impact on students' abilities to use scientific data in decision-making and on students' scientifically informed awareness of the environment. Educational levels: Graduate or professional

Advances in Evaporation and Evaporative Demand

The importance of evapotranspiration is well-established in different disciplines such as hydrology, agronomy, climatology, and other geosciences. Reliable estimates of evapotranspiration are also vital to develop criteria for in-season irrigation management, water resource allocation, long-term estimates of water supply, demand and use, design and management of water resources infrastructure, and evaluation of the effect of land use and management changes on the water balance. The objective of this Special Issue is to define and discuss several ET terms, including potential, reference, and actual (crop) ET, and present a wide spectrum of innovative research papers and case studies

Soil Surface Energy and Water Budgets during a Monsoon Season in Korea

Abstract In this study, attention has been focused on the climatology of some variables linked to the turbulent exchanges of heat and water vapor in the surface layer during a summer monsoon in Korea. In particular, the turbulent fluxes of sensible and latent heat, the hydrologic budget, and the soil temperatures and moistures have been analyzed. At large scale, because the measurements of those data are not only fragmentary and exiguously available but also infeasible for the execution of climatologic analyses, the outputs of a land surface scheme have been used as surrogate of observations to analyze surface layer processes [this idea is based on the methodology Climatology of Parameters at the Surface (CLIPS)] in the Korean monsoonal climate. Analyses have been made for the summer of 2005. As a land surface scheme, the land surface process model (LSPM) developed at the University of Torino, Italy, has been employed, along with the data collected from 635 Korean meteorological stations. The LSPM predictions showed good agreement with selected observations of soil temperature. Major results show that, during the rainfall season, soil moisture in the first tenths of centimeters frequently exceeds the field capacity, whereas most of the rainfall is "lost" as surface runoff. Evapotranspiration is the dominant component of the energy budget, sometimes even exceeding net radiation, especially during the short periods between the precipitation events; in these periods, daily mean soil temperatures are about 28°C or even more. The Gyeonggi-do region, the metropolitan area surrounding Seoul, shows some particularities when compared with the neighboring regions: solar radiation and precipitations are lower, causing high values of sensible heat flux and soil temperatures, and lower values of latent heat flux and soil moistures

Remote Sensing of Hydro-Meteorology

Flood/drought, risk management, and policy: decision-making under uncertainty. Hydrometeorological extremes and their impact on human–environment systems. Regional and nonstationary frequency analysis of extreme events. Detection and prediction of hydrometeorological extremes with observational and model-based approaches. Vulnerability and impact assessment for adaptation to climate change

시계열 InSAR 기법을 사용하여 비정상적 해수면 상승 기록을 보인 조위관측소의 수직지반변위 평가

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 지구환경과학부, 2021.8. 김덕진.Global sea level rise has been a serious threat to the low-lying coasts and islands around the world. It is important to understand the global and regional sea level changes for preventing the coastal zones. Tide gauges are installed around the world, which directly measures the change in sea level relative to the local datum. Sea level in the past three decades has risen to 1.8 mm/year compared to the sea level rise in the 20th century (3.35 mm/year), estimated by the Intergovernmental Panel on Climate Change (IPCC). However, along with the contributors of sea level rise, vertical land motion (VLM) is indeed an essential component for understanding the regional sea level change; however, its contribution remains still unclear. The VLM is referred to as change in elevation of land at tide gauge due to the regional and local processes by both natural and anthropogenic activities can deteriorate the sea level records and lead to spurious sea level acceleration. Assessing the vertical land motion at tide gauges with the accuracy of sub-millimeters is essential to reconstruct the global and regional sea level rise. Previous studies attempt to observe the vertical land movements at sparse locations through Global Positioning System (GPS). However, the VLM observed from the sparse GPS network makes the estimation uncertain. In this study, an alternative approach is proposed in this study to directly measure the relative vertical land motion including spatial and temporal variations through Synthetic Aperture Radar (SAR) data by using time-series SAR interferometric (InSAR) techniques. This work presents a contribution enhancing the estimation of VLM rates with high spatial resolution over large area using time-series InSAR analysis. First, the C-band Interferometric Wide-swath (IW) mode SAR data from the Sentinel-1 A/B satellite was used in this study to estimate the VLM rates of tide gauges. The Sentinel-1 A/B SAR data were obtained during the period between 2014/10 and 2020/12 (~ 6 years). Stanford Method for Persistent Scatterers – Persistent Scatterer Interferometry (StaMPS-PSI) time-series InSAR algorithm was initially applied to the case study: Pohang tide gauge in the Korean peninsula for monitoring the stability of tide gauge station and its VLM rates during 2014 ~ 2017. For the Pohang tide gauge site, SAR data acquired in both ascending and descending passes and derived the ground movement rates at tide gauge along the line-of-sight direction. The vertical movements from the collocated POHA GPS station were compared with the InSAR derived VLM rates for determining the correlation between the two methods. The VLM rates at the Pohang tide gauge site were -25.5 mm/year during 2014 ~ 2017. This VLM rate at Pohang tide gauge derived by StaMPS-PSI estimates were from the strong dominant scatterers along the coastal regions. Second, for the terrains, with few dominant scatterers and more distributed scatters, a short temporal InSAR pair selection approach was introduced, referred as Sequential StaMPS-Small baselines subset (StaMPS-SBAS) was proposed in this study. Sequential StaMPS-SBAS forms the interferograms of short temporal sequential order (n = 5) to increase the initial pixel candidates on the natural terrains in the vicinity of tide gauges. Sentinel-1 A/B SAR data over ten tide gauges in the Korean peninsula having different terrain conditions were acquired during 2014 ~ 2020; and employed with sequential StaMPS-SBAS to estimate the VLM rates and time-series displacements. The initial pixel density has been doubled and ~ 1.25 times the final coherent pixels identified over the conventional StaMPS-SBAS analysis. Third, the potential for the fully automatic estimation of time-series VLM rates by sequential StaMPS-SBAS analysis was investigated. A fully automatic processing module referred to as ‘Seq-TInSAR’, was developed which has three modules 1) automatically downloads Sentinel-1 Single look complex (SLC) data, precise orbit files, and Digital Elevation Model (DEM); 2) SLC pre-processor: extract bursts, fine Coregistration and stacking and, 3) Sequential StaMPS-SBAS processor: estimates the VLM rates and VLM time-series. Finally, the Seq-TInSAR module is applied to the 100 tide gauges that exhibit abnormal sea level trend with par global mean sea level average. For each tide gauge site, 60 ~ 70 Sentinel-1 A/B SLC scenes were acquired and 300 ~ 350 sequential interferograms were processed to estimate the VLM at tide gauge stations. The final quantitative VLM rates and time-series VLM are estimated for the selected tide gauges stations. Based on the VLM rates, the tide gauges investigated in this study are categorized into different VLM ranges. The in-situ GPS observations available at 12 tide gauge stations were compared with InSAR VLM rates and found strong agreement, which suggests the proposed approach more reliable in measuring the spatial and temporal variations of VLM at tide gauges.전 세계적으로 발생하는 해수면 상승은 저지대 해안과 도서 지역에 심각한 위협으로 작용한다. 해안 지역을 보호하기 위해 전 지구 및 해당 지역의 해수면 변화를 이해하는 것은 대단히 중요하다. 조위 관측소는 전 세계에 설치되어 해당 지역 기준에 따른 해수면 변화를 직접 측정한다. 지난 30 년간 해수면은 IPCC (정부 간 기후 변화 패널)가 추정한 20 세기의 해수면 상승 (3.35mm / 년)대비 1.8mm / 년 가까이 상승하였다. 그러나 해수면 상승의 원인과 함께 연직 지반 운동 (VLM)은 지역 해수면 변화를 이해하는 데 필수적인 요소이지만 그 기여도는 여전히 불분명하다. VLM은 자연 활동과 인간 활동 모두에 의한 지역적 변화로 인해 조위 관측소에서 지반의 고도 변화로 정의되며 해수면 변화 정확도을 악화시키고 유사 해수면 변화의 가속을 초래할 수 있다. 전 세계 및 지역 해수면 상승을 재구성하려면 1 밀리미터 미만의 정확도로 조위 관측소에서 VLM을 평가하는 것이 필수적이다. 이전 연구는 GPS (Global Positioning System)를 통해 제한된 위치에서 VLM 을 관측하려고 시도하였으나 국소적인 GPS 신호들로부터 관측된 VLM으로는 그 추정이 불확실하다. 본 연구에서는 시계열 SAR 간섭계 (InSAR) 기법을 이용하여 SAR (Synthetic Aperture Radar) 데이터를 통해 공간적, 시간적 변화를 포함한 상대적 VLM을 직접 측정하기 위한 대안적 접근 방식을 제안한다. 이 작업은 시계열 InSAR 분석을 사용하여 광대역에 걸쳐 높은 공간 해상도로 VLM 속도의 추정을 향상시키는 데 기여한다. 첫째로, Sentinel-1 A / B 위성의 C-band Interferometric Wide-swath (IW) 모드 SAR 영상이 본 연구에서 조위 관측소의 VLM 속도를 추정하는 데 사용되었다. Sentinel-1 A / B SAR 영상은 2014 년 10 월부터 2020 년 12 월까지 (~ 6 년) 기간 동안 수집되었다. 고정 산란체를 위한 스탠포드 기법 – 고정 산란 간섭계 (StaMPS-PSI) 시계열 InSAR 알고리즘이 한반도 포항 조위 관측소의 2014 ~ 2017 년 동안의 조위 관측소의 안정성과 VLM 속도를 모니터링하기 위해 적용되었다. 포항 조위 관측소 부지의 경우, 위성궤도의 상승 및 하강 경로로 획득한 SAR 영상을 통해 시선 방향을 따라 조위 관측소에서의 지면 이동 속도를 도출하였다. 포항 GPS 관측소의 연직 이동은 두 기법 간의 상관성를 판단하기 위해 InSAR기법으로부터 추정된 VLM 속도와 비교되었다. 포항 조위 관측소의 VLM 속도는 2014 ~ 2017 년의 기간 동안 -25.5mm / 년으로 관측되었다. StaMPS-PSI 추정에 의해 도출 된 포항 조위 관측소의 VLM 속도은 해안 지역의 강한 산란 체에서 기인한다. 둘째로, 강한 산란체가 수가 적고 분산된 산란체가 더 많은 지형의 경우, 본 연구에서 Sequential StaMPS-Small baselines (StaMPS-SBAS)이라는 하는 단기 InSAR 쌍의 선택에 의한 접근 방식이 제안되었다. Sequential StaMPS-SBAS는 짧은 시간 범위(n = 5)의 간섭계 영상을 형성하여 조위 관측소 부근의 자연 지형에서 변화가 적은 화소 선택을 증가시킨다. Sentinel-1 A / B SAR 영상은 2014 년 ~ 2020 년 사이에 서로 다른 지형 조건을 가진 한반도의 10 개 조위 관측소에서 수집되었으며, VLM 속도 및 시계열 변위를 추정하기 위해 Sequential StaMPS-SBAS와 함께 사용되었다. 초기 화소 밀도는 기존 StaMPS-SBAS 분석을 통해 확인 된 최종적인 불변화소 밀도의 약 1.25 배와 두 배로 도출되었다. 셋째로, Sequential StaMPS-SBAS 분석에 의한 시계열 VLM 비율의 완전한 자동 추정 가능성을 조사하였다. Seq-TInSAR라고하는 완전한 자동 처리 모듈이 개발되었으며, 3 개의 하위 모듈로 구성되어있다. 1) Sentinel-1 SLC (Single Look Complex) 영상, 정밀한 궤도 정보 및 DEM (Digital Elevation Model)의 자동 다운로드 2) SLC 전 처리기 : 영상 별 Burst 추출, 정밀한 통합 및 Stacking, 3) Sequential StaMPS-SBAS 프로세서 : VLM 속도 및 VLM 시계열 변위의 추정 마지막으로, Seq-TInSAR 모듈은 동위 평균 해수면 평균으로 비정상적인 해수면 추세를 보이는 100 개의 조위 관측소에 적용된다. 조위 관측소 지점별로 60 ~ 70 개의 Sentinel-1 A / B SLC 영상을 획득하고 300 ~ 350 개의 시계열 간섭계 영상을 처리하여 조위 관측소에서 VLM을 추정하였다. 정량적인 VLM 속도와 시계열 VLM은 선정한 조위 관측소에 대해 추정하였다. VLM 속도을 기반으로 본 연구에서 도출한 조위 관측소는 다양한 VLM 범위로 분류된다. 12 개의 조위 관측소에서 취득한 현장 GPS 관측 자료를 InSAR로부터 추정한 VLM 비율과 비교하여 강력한 상관성을 찾았고, 이는 본 연구에서 제안한 접근 방식이 조위 관측소에서 VLM의 공간적 및 시간적 변화를 측정하는데 신뢰할 수 있는 자료로 사용될 수 있음을 시사한다.Chapter 1. Introduction 1 1.1. Brief overview of sea-level rise 1 1.2. Motivations 4 1.3. Purpose of Research 9 1.4. Outline 12 Chapter 2. Sea Level variations and Estimation of Vertical land motion 14 2.1. Sea level variations 14 2.2. Sea level observations 14 2.3. Long term sea level estimation 19 2.4. Factors contributing tide gauge records: Vertical Land Motion 19 2.5. Brief overview of InSAR and Time-series SAR Interferometry 24 Chapter 3. Vertical Land Motion estimation at Tide gauge using Time-series PS-InSAR technique: A case study for Pohang tide gauge 36 3.1. Background 36 3.2. VLM estimation at Pohang tide gauge using StaMPS-PSI analysis 38 3.3. Development of StaMPS-SBAS InSAR using Sequential InSAR pair selection suitable for coastal environments 55 3.4. Discussion 80 Chapter 4. Application of time-series Sequential-SBAS InSAR for Vertical Land Motion estimation at selected tide gauges around the world using Sentinel-1 SAR data 85 4.1. Description of PSMSL tide gauge data 87 4.2. Sentinel-1 A/B SAR data acquisitions 92 4.3. Automatic Time-series InSAR processing module ”Seq-TInSAR” 93 4.4. Results: Estimation of vertical land motions at selected tide gauges 97 4.5. Comparison of InSAR results with GNSS observations 112 4.6. Discussion 125 Chapter 5. Conclusions and Future Perspectives 128 Abstract in Korean 133 Appendix – A 136 Appendix – B 146 Bibliography 151박

Monitoring daily evapotranspiration in Northeast Asia using MODIS and a regional Land Data Assimilation System

We applied an approach for daily estimation and monitoring of evapotranspiration (ET) over the Northeast Asia monsoon region using satellite remote sensing observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Frequent cloud cover results in a substantial loss of remote sensing information, limiting the capability of continuous ET monitoring for the monsoon region. Accordingly, we applied and evaluated a stand-alone MODIS ET algorithm for representative regional ecosystem types and an alternative algorithm to facilitate continuous regional ET estimates using surface meteorological inputs from the Korea Land Data Assimilation System (KLDAS) in addition to MODIS land products. The resulting ET calculations showed generally favorable agreement (root-mean-square error  \u3c 1.3 mm d−1) with respect to in situ measurements from eight regional flux tower sites. The estimated mean annual ET for 3 years (2006 to 2008) was approximately 362.0 ± 161.5 mm yr−1 over the Northeast Asia domain. In general, the MODIS and KLDAS-based ET (MODIS-KLDAS ET) results showed favorable performance when compared to tower observations, though the results were overestimated for a forest site by approximately 39.5% and underestimated for a cropland site in South Korea by 0.8%. The MODIS-KLDAS ET data were generally underestimated relative to the MODIS (MOD16) operational global terrestrial ET product for various biome types, excluding cropland; however, MODIS-KLDAS ET showed better agreement than MOD16 ET for forest and cropland sites in South Korea. Our results indicate that MODIS ET estimates are feasible but are limited by satellite optical-infrared remote sensing constraints over cloudy regions, whereas alternative ET estimates using continuous meteorological inputs from operational regional climate systems (e.g., KLDAS) provide accurate ET results and continuous monitoring capability under all-sky conditions

BESS를 이용한 한반도 광합성과 증발산의 시공간 패턴 분석

학위논문 (석사)-- 서울대학교 환경대학원 : 환경계획학과, 2013. 2. 이도원.Analysis on spatial and temporal patterns of gross primary productivity (GPP) and evapotranspiration (ET) is critical in understanding and predicting terrestrial carbon and water cycles. However, there have been a few studies which provide spatially and temporally continuous estimates of GPP and ET in the Korean Peninsula. In this study, spatial and temporal patterns of GPP and ET in the Korean Peninsula were studied by using a bio-physical model, Breathing Earth System Simulator (BESS). GPP and ET from BESS are sensitive to Leaf Area Index (LAI) which is one of important input variables of BESS. LAI refinement was conducted by using re-modified temporal and spatial filter (rTSF) and LAI refinement improved accuracy compared to LAI from BESS and raw MODIS. The simulations of 11-year (2001-2011) GPP and ET in the Korean Peninsula were performed by using refined LAI. BESS derived GPP and ET were verified with eddy covariance measurements at 4 sites and 5 sites, respectively. Also, BESS derived basin ET was evaluated against water balance derived ET at a basin scale. Both GPP and ET from BESS show high positive bias at GDK and GCK sites while BESS derived GPP and ET were comparable to eddy covariance measurement at other sites and water balance derived ET. The mean annual land GPP and ET over the eleven years (2001-2011) were 1,183 gC m-2 year-1and 491 mm year-1. Land cover change was one of major causes for interannual variation of GPP and ET. In dry year, ET at highland became more sensitive to canopy conductance than that in normal year. Spring and autumn droughts caused spring and autumn ET to become most sensitive to canopy conductance. The sensitivity of ET to available energy increased in summer due to clouds during the summer monsoon.I. Introduction 1 II. Methods 8 1. Site description 8 2. Description of BESS 10 3. Improvement of BESS 11 1) Reprocessing MODIS LAI data 11 2) Change in Land cover type 24 4. Evaluation 26 1) Evaluation method 26 2) Evaluation data 27 III. Results 29 1. Evaluation 29 1) Reprocessing MODIS LAI product 29 2) BESS derived GPP and ET 34 2. Analysis on Spatial and Temporal patterns 42 IV. Discussion 52 1. Evaluation of BESS. 52 2. Spatial and Temporal Patterns of GPP and ET 52 3. What controls evapotranspiration in Korea? 54 4. How do the contributions of sunlit and shaded leaves to GPP change in different season? 55 V. Conclusion 57 Reference 58 Acknowledgements 68Maste

PeRL : a circum-Arctic Permafrost Region Pond and Lake database

Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i. e., waterbodies with surface areas smaller than 1.0 x 10(4) m(2), have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1.4 x 10(6) km(2) across the Arctic, about 17% of the Arctic lowland (Peer reviewe