Rare observations of sprites and gravity waves supporting D, E, F-regions ionospheric coupling

We report rare simultaneous observations of columniform sprites and associated gravity waves (GWs) using the Transient Luminous Events (TLEs) camera and All-sky imager at Prayagraj (25.5° N, 81.9° E, geomag. lat. ~ 16.5° N), India. On 30 May 2014, a Mesoscale Convective System generated a group of sprites over the north horizon that reached the upper mesosphere. Just before this event, GWs (period ~ 14 min) were seen in OH broadband airglow (emission peak ~ 87 km) imaging that propagated in the direction of the sprite occurrence and dissipated in the background atmosphere thereby generating turbulence. About 9–14 min after the sprite event, another set of GWs (period ~ 11 min) was observed in OH imaging that arrived from the direction of the TLEs. At this site, we also record Very Low Frequency navigational transmitter signal JJI (22.2 kHz) from Japan. The amplitude of the JJI signal showed the presence of GWs with ~ 12.2 min periodicities and ~ 18 min period. The GWs of similar features were observed in the ionospheric Total Electron Content variations recorded at a nearby GPS site. The results presented here are important to understand the physical coupling of the troposphere with the lower and upper ionosphere through GWs.

An Analysis of the 3 May 2020 Low-Predictability Derecho Using a Convection-Allowing MPAS Ensemble

This study analyzes the low short-range predictability of the 3 May 2020 derecho using a 40-member convection-allowing Model for Prediction Across Scales (MPAS) ensemble. Elevated storms formed in south-central Kansas late at night and evolved into a progressive mesoscale convective system (MCS) during the morning while moving across southern Missouri and northern Arkansas, and affected western and middle Tennessee and southern Kentucky in the afternoon. The convective initiation (CI) in south-central Kansas, the organization of a dominant bow echo MCS and the MCS maintenance over Tennessee were identified as the three main predictability issues. These issues were explored using three MPAS ensemble members, observations and the Rapid Refresh analyses. The MPAS members were classified as successful or unsuccessful with regard to each predictability issue. CI in south-central Kansas was sensitive to the temperature and dewpoint profiles in low levels, which were associated with greater elevated thermodynamic instability and lower level of free convection in the successful member. The subsequent organization of a dominant bowing MCS was well predicted by the member that had more widespread convection in the early stages and no detrimental interaction with other simulated convective systems. Lastly, the inability of MPAS ensemble members to predict the MCS maintenance over western and middle Tennessee was linked to a dry bias in low levels and much lower thermodynamic instability ahead of the MCS compared to observations. This case demonstrates the challenges in operational forecasting of warm-season derecho-producing progressive MCSs, particularly when ensemble numerical weather prediction guidance solutions differ considerably.

Evidence for the breakdown of an Angkorian hydraulic system, and its historical implications for understanding the Khmer Empire

This paper examines the construction and design of a 7-km long embankment, probably builtfor King Jayavarman IV between 928 and 941 CE, as part of a new capital. We calculate thatthe capacities of the outlets were too small, and conclude that the embankment failed, probablywithin a decade of construction, so that the benefits of the reservoir stored by the embankmentand the access road on top of it were lessened substantially. We explain how the design wassub-optimal for construction, and that while the layout had a high aesthetic impact, theprocesses for ensuring structural integrity were poor. Simple and inexpensive steps to securethe weir were not undertaken. We speculate that this early failure may have contributed to thedecision to return the royal court and the capital of the Khmer Empire to the Angkor region,marking a critically important juncture in regional history.Abbreviations: APHRODITE, Asian Precipitation – Highly Resolved Observational DataIntegration Towards Evaluation (of Water Resources); ARI, annual recurrence interval; ASL,above sea level; DIAS, Data Integration and Analysis System; EFEO, École françaised'Extrême-Orient; GPR, ground penetrating radar; HEC-GeoRAS, Hydrologic EngineeringCenter: GIS tools for support of HEC-RAS; HEC-RAS, Hydrologic Engineering Center: RiverAnalysis System; HEC-HMS, Hydrologic Engineering Center: Hydrologic Modeling System;MCS, mesoscale convective system; RMSE, root mean square error; SRTM, NASA ShuttleRadar Topography Mission; TRMM, Tropical Rainfall Measuring Mission

Spatiotemporal variation of mesoscale convective system type persistent elongated convective system (PECS) in Indonesia

Research on Mesoscale Convective Systems (MCS) in Indonesia has been studied to identify the characteristics and distribution of MCS. Persistent Elongated Convective System (PECS) is one of the MCS types that can cause extreme weather. However, identifying the spatial and temporal variations of PECS in Indonesia has not been studied further. This study examines the Persistent Elongated Convective System (PECS) in Maritime Continent from 2010-2014. MERG Dataset with brightness temperature is used to identify PECS and input Grab ‘Em Tag ‘Em Graph ‘Em (GTG) tracking algorithm to gain a better understanding of spatiotemporal variation in Indonesia. Flood data from BNPB in Indonesia is used to find out the correlation between flood and PECS events in Indonesia. PECS events in 2010-2014 are 5574 events, which the transitional period (MAM and SON) has the most PECS events and longest duration of life. The PECS spread in the early morning on land and sea, while on day and nighttime, it is concentrated on land for the area of Java, Papua, and Southern Kalimantan. Java and Papua have the largest concentrated PECS events. The life phase of the PECS has two peaks or semidiurnal cycles, in the morning and nighttime. There are differences in peak times for each phase of the PECS on land and sea. In Indonesia, PECS has the smallest average maximum area than in the USA and China but has the longest duration and largest eccentricity. Based on flood data from BNPB, during 2010-2014, Java has the most flood. According to flood data and PECS events in Java, there is 6.72% of flood coincided with PECS events during the period.

Study of Mesoscale Convective Complex (MCC) and its impact over the Makassar Strait (case study: 9 December 2014)

A mesoscale Convective System (MCS) is a system consisting of groups of convective cells in the mesoscale. One of the largest types of MCS subclass is Mesoscale Convective Complex (MCC) occurred in the eastern part of the Makassar Strait near the Madjene and Polewali Mandar regions on 9 December 2014, morning to evening (09.00-15.00 LT). Using MTSAT-2 Satellite Imagery data, reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) interim era, the Global Satellite Mapping of Precipitation (GsMap) rainfall, sea surface temperature, surface air observation, and upper air observation, the author will examine the existence of MCC in the Makassar Strait in terms of atmospheric conditions when MCC enters the initial until extinct and the accompanying effects of precipitation. In general, it is known that the MCC formed in the waters of the Makassar Strait in the morning, and then it moved westward. The mechanism of its formation was through a process of convergence of the lower layers in the waters of the Makassar Strait and its surroundings to trigger the process of cloud formation. Warm thermal conditions also gave a big influence on the lower layers to the top and activate convective in the study area. Meanwhile, the MCC occurrence region also has high relative humidity, negative divergence values, and maximum vorticity values. The impact of the emergence of MCC on that date resulted in areas with very large humidity and cloud formation and produced rain in the surrounding area, in this case using rainfall data from Hasanuddin Meteorological Station, Makassar, South Sulawesi. With a duration of up to seven hours extinct, MCC in the Makassar Strait produces heavy rainfall in the Makassar Strait waters.

Asymmetric Structures of a Squall-Line MCS over Taiwan with Significant Hydraulic Jumps

On 19 April 2019, a mature squall-line mesoscale convective system (MCS) with the characteristics of a leading convective line and trailing stratiform landed on Taiwan, resulting in strong gust wind and heavy rainfall. This squall-line MCS became asymmetric after landfall on Taiwan. Two sets of idealized numerical simulations (mountain heights and low-level vertical wind shear) using the Weather Research and Forecasting (WRF) model were conducted to examine the impacts of realistic Taiwan topography on a squall-line MCS. Results showed numerous similarities between the idealized simulations and real-case observations. The low-level Froude number which considered the terrain height (Fmt) was calculated to examine the blocking effect of the Taiwan terrain, and the cold pool (determined by − 1.5 K isotherm) was found to be completely blocked by the 500-m height contour. The northeast-southwest orientation of the Snow Mountain Range (SMR), and the north–south orientation of the Central Mountain Range (CMR) led to the upwind side asymmetry. On the other hand, the lee-side asymmetry was associated with different intensities and occurrence locations of the hydraulic jump between the SMR and southern CMR, and the cold-pool Froude number (Fcp) indicated the flow-regime transition from subcritical to supercritical.

Identifikasi Fenomena Mesoscale Convective System (MCC) di Selat Karimata

Abstract—Indonesia located in the equatorial region which has potential to have a major impact on atmospheric physical conditions during extreme weather events such as the Mesoscale Convective Complex (MCC). MCC is a phenomenon that was first discovered by (Maddox, 1980) where this phenomenon is characterized by the presence of a quasi-circular (almost circular) cloud shield with an eccentricity of 0.7 with a cloud cover area of 100,000 km², the cloud core area covers 50,000 km² and cloud top temperature IR1 -52 ℃. These cloud conditions last for a minimum of 6 hours and cause severe weather and extreme rain. This study aims to identify the MCC phenomenon in the Karimata Strait on 19-20 September 2020 which caused heavy rains in parts of the West coast of Kalimantan and Bangka Island using Himawari-8 Satellite imagery data and the MATLAB application. The results showed that on September 19, MCC was identified at 09.00-19.00 UTC, then on September 20, MCC was identified at 16.00-23.00 UTC. At the time of the MCC event, Bangka and Pontianak regions experienced extreme rains recorded on AWS Digi Stamet Pontianak with rainfall reaching 43.4 mm/hour and ARG Lubuk Besar Bangka Tengah with rainfall reaching 16.8 mm/hour. Keywords: mesoscale convective complex (MCC), himawari-8, MATLAB Abstrak—Indonesia merupakan negara yang terletak diwilayah ekuator dimana berpotensi memiliki dampak besar terhadap kondisi fisik atmosfer saat terjadi cuaca ekstrem seperti Mesoscale Convective Complex (MCC). MCC merupakan fenomena yang pertama kali ditemukan oleh (Maddox, 1980) dimana fenomena ini dicirikan dengan adanya perisai awan yang berbentuk quasi circular (hampir lingkaran) dengan eksentrisitas ≥ 0,7 dengan luas area selimut awan ≥ 100.000 km² , luas area inti awan mencakup ≥ 50.000 km² serta suhu puncak awan IR1 ≤ -52 ℃. Kondisi awan tersebut bertahan minimun selama 6 jam dan menyebabkan cuaca buruk dan hujan ekstrem. Penelitian ini bertujuan untuk mengidentifikasi fenomena MCC di Selat Karimata pada Tanggal 19-20 September 2020 yang menyebabkan hujan lebat di sebagian wilayah Kalimantan bagian pesisir Barat dan Pulau Bangka menggunakan data citra Satelit Himawari-8 dan aplikasi MATLAB. Hasil penelitian menunjukkan pada tanggal 19 September, MCC teridentifikasi pada pukul 09.00-19.00 UTC selanjutnya tanggal 20 September 2020 MCC teridentifikasi pada pukul 16.00-23.00 UTC. Pada saat peristiwa MCC, wilayah Bangka dan Pontianak mengalami hujan ekstrem yang tercatat pada AWS Digi Stasiun Meteorologi Pontianak dengan curah hujan mencapai 43,4 mm/jam dan ARG Lubuk Besar Bangka Tengah dengan curah hujan mencapai 16,8 mm/jam. Kata kunci: mesoscale convective complex (MCC), himawari-8, MATLAB

Bias Correction, Anonymization, and Analysis of Smartphone Pressure Observations Using Machine Learning and Multi-Resolution Kriging

With over a billion smartphones capable of measuring atmospheric pressure, a global mesoscale surface pressure network based on smartphone pressure sensors may be possible if key technical issues are solved, including collection technology, privacy and bias correction. To overcome these challenges, a novel framework was developed for the anonymization and bias correction of smartphone pressure observations (SPOs) and was applied to billions of SPOs from The Weather Company (IBM). Bias correction using machine learning reduced the errors of anonymous (ANON) SPOs and uniquely identifiable (UID) SPOs by 43% and 57%, respectively. Applying multi-resolution kriging, gridded analyses of bias-corrected smartphone pressure observations were made for an entire year (2018), using both anonymized (ANON) and non-anonymized (UID) observations. Pressure analyses were also generated using conventional (MADIS) surface pressure networks. Relative to MADIS analyses, ANON and UID smartphone analyses reduced domain-average pressure errors by 21% and 31%. The performance of smartphone and MADIS pressure analyses was evaluated for two high-impact weather events: the landfall of Hurricane Michael and a long-lived mesoscale convective system. For these two events, both anonymized and non-anonymized smartphone pressure analyses better captured the spatial structure and temporal evolution of mesoscale pressure features than the MADIS analyses.