Black carbon (BC) aerosol particles, when being in sufficient amount in the Earth’s atmosphere, significantly influence its radiation balance and intensively deplete ozone by heterogeneous chemical reactions. There are many sources of BC in the troposphere: bio- and fossil-fuel burning, forest and bush fires, power generation and industrial processes, engines, etc. Aircraft emissions are widely assumed to be the principal source of BC nanoparticles in the stratosphere. In this paper, we make a hypothesis that Plinian eruptions with VEI ≥ 5 are a strong occasional source of long-lived BC in the stratosphere and suggest a possible mechanism of BC formation in volcanic conduits during the eruptions. Based on this hypothesis, and using the 1991 Pinatubo eruption (VEI = 6) as an example, we roughly estimate CBC and number concentration of BC particles NBC, which are required to cause ozone depletion events in the tropical stratosphere (at altitudes where ozone depletion cannot occur due to the presence of volcanic sulfuric acid aerosols). For this purpose, we use vertical ozone profiles obtained over the tropical station Hilo (19.72° N, 155.11° W; Hawaii) in September and November 1992. The September CBC and NBC values, we calculated for BC particles of mean radius 120 nm at an altitude of ~20.5 km, are 35.4 ±30.6 ng/m3 and (2.2±1.9)×106 particles/m3, respectively. The November CBC and NBC values for BC particles of mean radius 40 nm at an altitude of ~30 km are 25.3 ±7.8 ng/m3 and (4.2±1.3)×107 particles/m3, respectively.
KEYWORDS: Calibration, Raman spectroscopy, LIDAR, Temperature metrology, Troposphere, Solids, Climatology, High temperature raman spectroscopy, Data modeling, Signal detection
We present a temporal stability study of the calibration coefficients of two nonlinear calibration functions which are used for temperature retrievals in the pure rotational Raman (PRR) lidar technique. These functions represent the special cases of the general calibration function that takes into account the collisional broadening of all N2 and O2 PRR lines in the troposphere. The coefficients stability is studied on the examples of vertical tropospheric temperature profiles (3–9 km) retrieved on 1, 6, 7, and 8 April 2015. The temperature profiles were retrieved from nighttime lidar measurements made in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) using the IMCES PRR lidar. The lidar was developed in the Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences (IMCES SB RAS). The validity of usage of the calibration coefficients averaged over some period of monitoring for temperature profile retrievals is discussed.
KEYWORDS: LIDAR, Calibration, Temperature metrology, Raman spectroscopy, Troposphere, Statistical analysis, Remote sensing, Data modeling, Climatology, Iterated function systems
We present and examine two three-coefficient calibration functions to be used for the tropospheric temperature retrievals via the pure rotational Raman (PRR) lidar technique. These functions are the special cases of the general analytical calibration function in the PRR lidar technique. The general function special cases take into account the collisional (pressure) broadening of all individual atmospheric N2 and O2 PRR lines in varying degrees. We apply these two special cases to real lidar remote sensing data and compare nighttime temperature profiles retrieved using these calibration functions to the profiles retrieved using other known ones. The absolute statistical uncertainties of temperature retrieval are also given in an analytical form. Lidar measurements data, obtained in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) using the IMCES PRR lidar at λ = 354.67 nm on 1 April 2015, were used for the tropospheric temperature retrievals (3–12 km).
We present the general calibration function for temperature retrievals in the cloud-free troposphere using pure rotational Raman (PRR) lidars under the condition of the laser-beam receiver-field-of-view complete overlap. The function is derived within the framework of the semiclassical theory and takes account of the broadened by collision effects elastic backscattered signal leakage into the nearest (to the laser line) lidar PRR channel. The two simplest nonlinear special cases of the general calibration function are considered to be applied in the temperature retrieval algorithm. The vertical temperature profiles retrieved from nighttime lidar measurements in Tomsk (56.48°N, 85.05°E), on October 2, 2014, are given as an example. The measurements were performed using a PRR lidar designed in Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences (IMCES SB RAS) for lower-atmosphere temperature-profile retrievals.
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