Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Altitude and Particle Size Measurements of Noctilucent Clouds by RGB
  Photometry: Radiative Transfer and Correlation Analysis   Noctilucent or polar mesospheric clouds have become visually brighter and
occurred more frequently during the recent years and decades. The study of
possible reasons and relations with climate changes requires data on long-time
trends of mean particle size and altitude. Extended worldwide observational
data is a good tool for this, and it can be provided by simple RGB-photometry
using widely distributed all-sky cameras. Based on observations of bright
expanded clouds in summer 2020 and 2021, the method of mean particle size
determination is developed, results are validated using the radiative transfer
model. The procedure also allows finding the effective 'umbral' altitude of
clouds. The correlation of size and altitude of particles is compared with
existing lidar data and models of particle growth.

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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
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The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org