Evaluation of the Performance Characteristics of the Lightning Imaging Sensor

AbstractThe Lightning Imaging Sensor (LIS) that was on board the Tropical Rainfall Measuring Mission (TRMM) satellite captured optical emissions produced by lightning. In this work, we quantify and evaluate the LIS performance characteristics at both the pixel level of LIS events and contiguous clusters of events known as groups during a recent 2-yr period. Differences in the detection threshold among the four quadrants in the LIS pixel array produce small but meaningful differences in their optical characteristics. In particular, one LIS quadrant (Q1, X ≥ 64; Y ≥ 64) detects 15%–20% more lightning events than the others because of a lower detection threshold. Sensitivity decreases radially from the center of the LIS array to the edges because of sensor optics. The observed falloff behavior is larger on orbit than was measured during the prelaunch laboratory calibration and is likely linked to changes in cloud scattering pathlength with instrument viewing angle. Also, a two-season comparison with the U.S. National Lightning Detection Network (NLDN) has uncovered a 5–7-km north–south LIS location offset that changes sign because of periodic TRMM yaw maneuvers. LIS groups and flashes that had any temporally and spatially corresponding NLDN reports (i.e., NLDN reported the radio signals from the same group and/or from other groups in the same flash) tended to be spatially larger and last longer (only for flashes) than the overall population of groups/flashes.

Download Full-text

Film Thickness-Profile Measurement Using Iterative Peak Separation Structured Illumination Microscopy

Applied Sciences ◽

10.3390/app11073023 ◽

2021 ◽

Vol 11 (7) ◽

pp. 3023

Author(s):

Kejun Yang ◽

Chenhaolei Han ◽

Jinhua Feng ◽

Yan Tang ◽

Zhongye Xie ◽

...

Keyword(s):

Modulation Depth ◽

Thickness Distribution ◽

Detection Threshold ◽

Profile Measurement ◽

Structured Illumination ◽

Structured Illumination Microscopy ◽

Separation Algorithm ◽

Peak Separation ◽

Lower Detection ◽

Depth Response

The surface and thickness distribution measurement for transparent film is of interest for electronics and packaging materials. Structured illumination microscopy (SIM) is a prospective technique for measuring film due to its high accuracy and efficiency. However, when the distance between adjacent layers becomes close, the peaks of the modulation depth response (MDR) start to overlap and interfere with the peak extraction, which restricts SIM development in the field of film measurement. In this paper, an iterative peak separation algorithm is creatively applied in the SIM-based technique, providing a precise peak identification even as the MDR peaks overlap and bend into one. Compared with the traditional method, the proposed method has a lower detection threshold for thickness. The experiments and theoretical analysis are elaborated to demonstrate the feasibility of the mentioned method.

Download Full-text

Spatiotemporal Variability of Lightning Flash Distribution over Sri Lanka

International Letters of Chemistry Physics and Astronomy ◽

10.18052/www.scipress.com/ilcpa.82.1 ◽

2019 ◽

Vol 82 ◽

pp. 1-13

Author(s):

U.G.Dilaj Maduranga ◽

Mahesh Edirisinghe ◽

L. Vimukthi Gamage

Keyword(s):

Sri Lanka ◽

Monsoon Season ◽

Tropical Rainfall Measuring Mission ◽

Spatiotemporal Variability ◽

Spatial And Temporal Variation ◽

Lightning Flash ◽

Northeast Monsoon ◽

Time Period ◽

Total Lightning ◽

Imaging Sensor

The variation of the lightning activities over Sri Lanka and surrounded costal belt (5.750N-10.000N and 79.50E-89.000E) is studied using lightning flash data of Lightning Imaging Sensor (LIS) which was launched in November 1997 for NASA’s Tropical Rainfall Measuring Mission (TRMM). The LIS data for the period of 1998 to 2014 are considered for this study. The spatial and temporal variation of lightning activities is investigated and respective results are presented. The diurnal variation over the studied area presents that maximum and minimum flash count recorded at 1530-1630 Local Time (10-11UTC) and 0530-0630LT (00-01UTC) respectively. Maximum lightning activities over the observed area have occurred after the 1330LT (08UTC) in every year during the considered time period. The seasonal variation of the lightning activities shows that the maximum lightning activities happened in First inter monsoon season (March to April) with 30.90% total lightning flashes and minimum lightning activities recorded in Northeast monsoon season (December to February) with 8.51% of total lightning flashes. Maximum flash density of 14.37fl km-2year-1 was observed at 6.980N/80.160E in First inter monsoon season. These seasonal lighting activities are agree with seasonal convective activities and temperature variation base on propagation of Intra-Tropical Convection Zone over the studied particular area. Mean monthly flash count presents a maximum in the month of April with 29.12% of lightning flashes. Variation pattern of number of lightning activities in month of April shows a tiny increment during the time period of 1998 to 2014. Maximum annual flash density of 28.09fl km-2yr-1 was observed at 6.980N/80.170E. The latitudinal variation of the lightning flash density is depicted that extreme lightning activities have happened at the southern part of the county and results show that there is a noticeable lack of lightning activities over the surrounded costal belt relatively landmass.

Download Full-text

Preliminary Observations from the China Fengyun-4A Lightning Mapping Imager and Its Optical Radiation Characteristics

Remote Sensing ◽

10.3390/rs12162622 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2622 ◽

Cited By ~ 1

Author(s):

Wen Hui ◽

Wenjuan Zhang ◽

Weitao Lyu ◽

Pengfei Li

Keyword(s):

Data Processing ◽

Optical Radiation ◽

Monsoon Season ◽

Tropical Rainfall Measuring Mission ◽

Radiation Characteristics ◽

Southeastern China ◽

Northeastern India ◽

Satellite Platform ◽

Variation Characteristics ◽

Imaging Sensor

The Fengyun-4A (FY-4A) Lightning Mapping Imager (LMI) is the first satellite-borne lightning imager developed in China, which can detect lightning over China and its neighboring regions based on a geostationary satellite platform. In this study, the spatial distribution and temporal variation characteristics of lightning activity over China and its neighboring regions were analyzed in detail based on 2018 LMI observations. The observation characteristics of the LMI were revealed through a comparison with the Tropical Rainfall Measuring Mission (TRMM)-Lightning Imaging Sensor (LIS) and World Wide Lightning Location Network (WWLLN) observations. Moreover, the optical radiation characteristics of lightning signals detected by the LMI were examined. Factors that may affect LMI detection were discussed by analyzing the differences in optical radiation characteristics between LMI and LIS flashes. The results are as follows. Spatially, the flash density distribution pattern detected by the LMI was similar to those detected by the LIS and WWLLN. High-flash density regions were mainly concentrated over Southeastern China and Northeastern India. Temporally, LMI flashes exhibited notable seasonal and diurnal variation characteristics. The LMI detected a concentrated lightning outbreak over Northeastern India in the premonsoon season and over Southeastern China in the monsoon season, which was consistent with LIS and WWLLN observations. LMI-observed diurnal peak flash rates occurred in the afternoon over most of the regions. There was a “stepwise” decrease in the LMI-observed optical radiance, footprint size, duration, and number of groups per flash, from the ocean to the coastal regions to the inland regions. LMI flashes exhibited higher optical radiance but lasted for shorter durations than LIS flashes. LMI observations are not only related to instrument performance but are also closely linked to onboard and ground data processing. In future, targeted improvements can be made to the data processing algorithm for the LMI to further enhance its detection capability.

Download Full-text

Piezoresistive Carbon Nanofiber-Based Cilia-Inspired Flow Sensor

Nanomaterials ◽

10.3390/nano10020211 ◽

2020 ◽

Vol 10 (2) ◽

pp. 211 ◽

Cited By ~ 1

Author(s):

Debarun Sengupta ◽

Duco Trap ◽

Ajay Giri Prakash Kottapalli

Keyword(s):

Carbon Nanofiber ◽

Detection Threshold ◽

Flow Sensor ◽

Oxygen Intake ◽

Mems Devices ◽

Flow Sensors ◽

Flow Monitoring ◽

Flow Sensing ◽

Artificial Cilia ◽

Lower Detection

Evolving over millions of years, hair-like natural flow sensors called cilia, which are found in fish, crickets, spiders, and inner ear cochlea, have achieved high resolution and sensitivity in flow sensing. In the pursuit of achieving such exceptional flow sensing performance in artificial sensors, researchers in the past have attempted to mimic the material, morphological, and functional properties of biological cilia sensors, to develop MEMS-based artificial cilia flow sensors. However, the fabrication of bio-inspired artificial cilia sensors involves complex and cumbersome micromachining techniques that lay constraints on the choice of materials, and prolongs the time taken to research, design, and fabricate new and novel designs, subsequently increasing the time-to-market. In this work, we establish a novel process flow for fabricating inexpensive, yet highly sensitive, cilia-inspired flow sensors. The artificial cilia flow sensor presented here, features a cilia-inspired high-aspect-ratio titanium pillar on an electrospun carbon nanofiber (CNF) sensing membrane. Tip displacement response calibration experiments conducted on the artificial cilia flow sensor demonstrated a lower detection threshold of 50 µm. Furthermore, flow calibration experiments conducted on the sensor revealed a steady-state airflow sensitivity of 6.16 mV/(m s−1) and an oscillatory flow sensitivity of 26 mV/(m s−1), with a lower detection threshold limit of 12.1 mm/s in the case of oscillatory flows. The flow sensing calibration experiments establish the feasibility of the proposed method for developing inexpensive, yet sensitive, flow sensors; which will be useful for applications involving precise flow monitoring in microfluidic devices, precise air/oxygen intake monitoring for hypoxic patients, and other biomedical devices tailored for intravenous drip/urine flow monitoring. In addition, this work also establishes the applicability of CNFs as novel sensing elements in MEMS devices and flexible sensors.

Download Full-text

Investigation of Lightning Distribution Using LIS Data from TRMM Satellite

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.695.836 ◽

2014 ◽

Vol 695 ◽

pp. 836-839

Author(s):

Norbayah Yusop ◽

Siti Hawa Zainal ◽

Nor Azlan Mohd Aris ◽

S.A.M. Chachuli ◽

Mawarni Mohamed Yunus

Keyword(s):

Initial Data ◽

Lightning Discharge ◽

Winter Season ◽

Tropical Rainfall Measuring Mission ◽

Washington Dc ◽

Spring Season ◽

Seasonal Basis ◽

Earth’S Climate ◽

Total Lightning ◽

Imaging Sensor

This paper presents an investigation on lightning distribution using Lightning Imaging Sensor (LIS) data from Tropical Rainfall Measuring Mission (TRMM) satellite. The investigation is carried out on distribution and variability of total lightning occurred in the area of Washington DC (38.54°N, 77.2°W) during January to April 2011. LIS captures emissions that occurred in the atmosphere which emitted by lightning discharge by covering the most between ±35o in latitude. The lightning distributions are characterized based on monthly, daily, hourly and seasonal basis. The maps of global distribution of lightning flashes have been used as initial data. This analysis shows that a total number of 3.5 million flashes were detected during four months observation. The highest number of flashes recorded in April is about 3.4 million flashes compared to the 3,993 flashes in January. In terms of seasonal, this observation show that the spring season during March and April has highest occurrence of lightning which is 53.2% compared to the winter season in January and February which only 46.8%. This study can provides expected variations of the lightning distribution on the diurnal and seasonal basis, thus make it useful in describing the Earth’s climate.

Download Full-text

Where the Least Rainfall Occurs in the Sahara Desert, the TRMM Radar Reveals a Different Pattern of Rainfall Each Season

Journal of Climate ◽

10.1175/jcli-d-14-00145.1 ◽

2014 ◽

Vol 27 (18) ◽

pp. 6919-6939 ◽

Cited By ~ 11

Author(s):

Owen A. Kelley

Keyword(s):

Tropical Rainfall Measuring Mission ◽

Seasonal Patterns ◽

Sahara Desert ◽

Precipitation Radar ◽

Light Rain ◽

Rain Gauges ◽

The North ◽

Imaging Sensor ◽

Summer Rain ◽

Rainfall Climatology

Abstract Some previous studies were unable to detect seasonal organization to the rainfall in the Sahara Desert, while others reported seasonal patterns only in the less-arid periphery of the Sahara. In contrast, the precipitation radar on the Tropical Rainfall Measuring Mission (TRMM) satellite detects four rainy seasons in the part of the Sahara where the TRMM radar saw the least rainfall during a 15-yr period (1998–2012). According to the TRMM radar, approximately 20°–27°N, 22°–32°E is the portion of the Sahara that has the lowest average annual rain accumulation (1–5 mm yr−1). Winter (January and February) has light rain throughout this region but more rain to the north over the Mediterranean Sea. Spring (April and May) has heavier rain and has lightning observed by the TRMM Lightning Imaging Sensor (LIS). Summer rain and lightning (July and August) occur primarily south of 23°N. At a maximum over the Red Sea, autumn rain and lightning (October and November) can be heavy in the northeastern portion of the study area, but these storms are unreliable: that is, the TRMM radar detects such storms in only 6 of the 15 years. These four rainy seasons are each separated by a comparatively drier month in the monthly rainfall climatology. The few rain gauges in this arid region broadly agree with the TRMM radar on the seasonal organization of rainfall. This seasonality is reason to reevaluate the idea that Saharan rainfall is highly irregular and unpredictable.

Download Full-text

Laboratory Calibration of the Optical Transient Detector and the Lightning Imaging Sensor

Journal of Atmospheric and Oceanic Technology ◽

10.1175/1520-0426(2000)017<0905:lcotot>2.0.co;2 ◽

2000 ◽

Vol 17 (7) ◽

pp. 905-915 ◽

Cited By ~ 25

Author(s):

William J. Koshak ◽

Mike F. Stewart ◽

Hugh J. Christian ◽

James W. Bergstrom ◽

John M. Hall ◽

...

Keyword(s):

Laboratory Calibration ◽

Imaging Sensor ◽

Optical Transient

Download Full-text

Rainfall Climate Regimes: The Relationship of Regional TRMM Rainfall Biases to the Environment

Journal of Applied Meteorology and Climatology ◽

10.1175/jam2331.1 ◽

2006 ◽

Vol 45 (3) ◽

pp. 434-454 ◽

Cited By ~ 130

Author(s):

Wesley Berg ◽

Tristan L'Ecuyer ◽

Christian Kummerow

Keyword(s):

Detection Threshold ◽

Tropical Rainfall Measuring Mission ◽

Temporal Variations ◽

Critical Examination ◽

Simple Relationship ◽

High Concentrations ◽

Microwave Imager ◽

Highly Correlated ◽

Rainfall Detection ◽

Rainfall Estimates

Abstract Intercomparisons of satellite rainfall products have historically focused on the issue of global mean biases. Regional and temporal variations in these biases, however, are equally important for many climate applications. This has led to a critical examination of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and precipitation radar (PR). Because of the time-dependent nature of these biases, it is not possible to apply corrections based on regionally defined characteristics. Instead, this paper seeks to relate PR–TMI differences to physical variables that can lead to a better understanding of the mechanisms responsible for the observed differences. To simplify the analysis, issues related to differences in rainfall detection and intensity are investigated separately. For clouds identified as raining by both sensors, differences in rainfall intensity are found to be highly correlated with column water vapor. Adjusting either TMI or PR rain rates based on this simple relationship, which is relatively invariant over both seasonal and interannual time scales, results in a 65%–75% reduction in the rms difference between seasonally averaged climate rainfall estimates. Differences in rainfall detection are most prominent along the midlatitude storm tracks, where widespread, isolated convection trailing frontal systems is often detected only by the higher-resolution PR. Conversely, over the East China Sea clouds below the ∼18-dBZ PR rainfall detection threshold are frequently identified as raining by the TMI. Calculations based on in situ aerosol data collected south of Japan support a hypothesis that high concentrations of sulfate aerosols may contribute to abnormally high liquid water contents within nonprecipitating clouds in this region.

Download Full-text