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  • Author or Editor: B. L. Li x
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A. M. Makarieva
,
V. G. Gorshkov
,
A. V. Nefiodov
,
D. Sheil
,
A. D. Nobre
,
P. Bunyard
, and
B.-L. Li

Abstract

Precipitation generates small-scale turbulent air flows—the energy of which ultimately dissipates to heat. The power of this process has previously been estimated to be around 2–4 W m−2 in the tropics: a value comparable in magnitude to the dynamic power of global atmospheric circulation. Here it is suggested that the true value is approximately half the value of this previous estimate. The result reflects a revised evaluation of the mean precipitation pathlength HP . The dependence of HP on surface temperature, relative humidity, temperature lapse rate, and degree of condensation in the ascending air were investigated. These analyses indicate that the degree of condensation, defined as the relative change of the saturated water vapor mixing ratio in the region of condensation, is a major factor determining HP . From this theory the authors develop an estimate indicating that the mean large-scale rate of frictional dissipation associated with total precipitation in the tropics lies between 1 and 2 W m−2 and show empirical evidence in support of this estimate. Under terrestrial conditions frictional dissipation is found to constitute a minor fraction of the dynamic power of condensation-induced atmospheric circulation, which is estimated to be at least 2.5 times larger. However, because HP increases with increasing surface temperature Ts , the rate of frictional dissipation would exceed the power of condensation-induced dynamics, and thus block major circulation, at Ts ≳ 320 K in a moist adiabatic atmosphere.

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Comments on “An Evaluation of Hurricane Superintensity in Axisymmetric Numerical Models”

A. M. Makarieva
,
A. V. Nefiodov
,
D. Sheil
,
A. D. Nobre
,
A. V. Chikunov
,
G. Plunien
, and
B.-L. Li

Abstract

In a recent paper Rousseau-Rizzi and Emanuel (2019) presented a derivation of an upper limit on maximum hurricane velocity at the ocean surface. This derivation was based on a consideration of an infinitely narrow (differential) Carnot cycle with the warmer isotherm at the point of the maximum wind velocity. Here we show that this derivation neglected a significant term describing the kinetic energy change in the outflow. Additionally, we highlight the importance of a proper accounting for the power needed to lift liquid water. Finally, we provide a revision to the formula for surface fluxes of heat and momentum showing that, if we accept the assumptions adopted by Rousseau-Rizzi and Emanuel (2019), the resulting velocity estimate does not depend on the flux of sensible heat.

Open access
A. M. Makarieva
,
V. G. Gorshkov
,
A. D. Nobre
,
A. V. Nefiodov
,
D. Sheil
,
P. Nobre
, and
B.-L. Li

Abstract

Here we respond to Jaramillo et al.’s recent critique of condensation-induced atmospheric dynamics (CIAD). We show that CIAD is consistent with Newton’s laws while Jaramillo et al.’s analysis is invalid. To address implied objections, we explain our different formulations of “evaporative force.” The essential concept of CIAD is condensation’s role in powering atmospheric circulation. We briefly highlight why this concept is necessary and useful.

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L. A. Remer
,
Y. J. Kaufman
,
D. Tanré
,
S. Mattoo
,
D. A. Chu
,
J. V. Martins
,
R.-R. Li
,
C. Ichoku
,
R. C. Levy
,
R. G. Kleidman
,
T. F. Eck
,
E. Vermote
, and
B. N. Holben

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard both NASA’s Terra and Aqua satellites is making near-global daily observations of the earth in a wide spectral range (0.41–15 μm). These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode, and several derived parameters including reflected spectral solar flux at the top of the atmosphere. Over the ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 to 2.13 μm. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral irradiance contributed by the aerosol, mass concentration, and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of Aerosol Robotic Network (AERONET) data gleaned from 132 AERONET stations. Eight thousand MODIS aerosol retrievals collocated with AERONET measurements confirm that one standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of Δτ = ±0.03 ±0.05τ over ocean and Δτ = ±0.05 ± 0.15τ over land. Two hundred and seventy-one MODIS aerosol retrievals collocated with AERONET inversions at island and coastal sites suggest that one standard deviation of MODIS effective radius retrievals falls within Δr eff = ±0.11 μm. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.

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Philip A. Feiner
,
William H. Brune
,
David O. Miller
,
Li Zhang
,
Ronald C. Cohen
,
Paul S. Romer
,
Allen H. Goldstein
,
Frank N. Keutsch
,
Kate M. Skog
,
Paul O. Wennberg
,
Tran B. Nguyen
,
Alex P. Teng
,
Joost DeGouw
,
Abigail Koss
,
Robert J. Wild
,
Steven S. Brown
,
Alex Guenther
,
Eric Edgerton
,
Karsten Baumann
, and
Juliane L. Fry

Abstract

The chemical species emitted by forests create complex atmospheric oxidation chemistry and influence global atmospheric oxidation capacity and climate. The Southern Oxidant and Aerosol Study (SOAS) provided an opportunity to test the oxidation chemistry in a forest where isoprene is the dominant biogenic volatile organic compound. Hydroxyl (OH) and hydroperoxyl (HO2) radicals were two of the hundreds of atmospheric chemical species measured, as was OH reactivity (the inverse of the OH lifetime). OH was measured by laser-induced fluorescence (LIF) and by taking the difference in signals without and with an OH scavenger that was added just outside the instrument’s pinhole inlet. To test whether the chemistry at SOAS can be simulated by current model mechanisms, OH and HO2 were evaluated with a box model using two chemical mechanisms: Master Chemical Mechanism, version 3.2 (MCMv3.2), augmented with explicit isoprene chemistry and MCMv3.3.1. Measured and modeled OH peak at about 106 cm−3 and agree well within combined uncertainties. Measured and modeled HO2 peak at about 27 pptv and also agree well within combined uncertainties. Median OH reactivity cycled between about 11 s−1 at dawn and about 26 s−1 during midafternoon. A good test of the oxidation chemistry is the balance between OH production and loss rates using measurements; this balance was observed to within uncertainties. These SOAS results provide strong evidence that the current isoprene mechanisms are consistent with measured OH and HO2 and, thus, capture significant aspects of the atmospheric oxidation chemistry in this isoprene-rich forest.

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