This study explores the maximum bathymetric capabilities of the ICESat-2 in coastal environments, with a particular focus on the impact of cirrus cloud thickness. Utilizing MODTRAN simulations for atmospheric transmittance under various cloud conditions, we integrate these with a maximum bathymetric depth model to quantitatively assess this impact. Our results indicate a significant decrease in detection depth with increasing cloud thickness, culminating in complete signal attenuation at cloud thicknesses of 3-4 km. Furthermore, simulations reveal that the FF phase function model outperforms OTHG and TTHG models, exhibiting the lowest Mean Absolute Error (MAE) and Mean Relative Error (MRE) in the Puerto Rico and Virgin Islands study sub-areas. This research provides critical insights into the capabilities and limitations of spaceborne lidar in coastal bathymetry, highlighting the importance of atmospheric conditions in remote sensing applications.
A low-cost NO2 trace concentration measuring device based on a cavity ring-down spectroscopy (CRDS) technique is presented. We theoretically and experimentally demonstrate that, if the nonresonant direct reflection is effectively isolated, an inexpensive broadband diode laser (LD) can excite multiple cavity modes and stabilize the cavity output signal with an optical feedback (OF) method. To improve the measuring accuracy for low concentrations of NO2 gases, we also design and machine a cavity with several mixing rooms. Several standard concentrations NO2 gases are used to test the apparatus. The results prove a great agreement between measured and theoretical values over the full range.
With the outbreak of COVID-19,masks,as the most important personal protective equipment, its necessity and importance becomes evident. Particle protective performance, as the key index of masks, the accuracy of its test result is very important. In this study, based on the high-precision photometer, the calibration method of particle protective performance testers for mask is studied. The protective performance is evaluated by the percentage of particle concentration reduction of before and after the mask. Photometric method is a relatively mature technology of particle concentration measurement, with advantages of portability and quick response. In our study, two photometers are used in the calibration. In order to ensure the accuracy, it is necessary to calibrate the two photometers first. Aerosol with concentrations about 1, 10, 20 and 30 mg/m3 is generated in the test chamber, respectively. The filter weight method is used to measure the concentration in the test chamber as the standard values. Within the weighing time, the concentration test results measured by the two photometers are recorded and calibrated with the concentration results measured by the weight method. For the two calibrated photometers, one is used to measure the particle concentration in the test chamber, the other is used to measure the particle concentration in the mask which is attached to the head mold. In this way, the particle protective performance value measured by the instrument can be calibrated. In our experiment, the extended uncertainty of the calibration results are lower than 3%.
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