Influence of ENSO and MJO on the zonal structure of tropical tropopause inversion layer using high-resolution temperature profiles retrieved from COSMIC GPS Radio Occultation
<p>Using COSMIC GPS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with the height resolution of about 0.1 km in the upper troposphere and lower stratosphere (UTLS). We investigated the distribution of static stability (<...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/6985/2019/acp-19-6985-2019.pdf |
| Summary: | <p>Using COSMIC GPS Radio Occultation (RO) observations from
January 2007 to December 2016, we retrieved temperature profiles with the
height resolution of about 0.1 km in the upper troposphere and lower
stratosphere (UTLS). We investigated the distribution of static stability
(<span class="inline-formula"><i>N</i><sup>2</sup></span>) and the zonal structure of the tropopause inversion layer (TIL) in
the tropics, where a large change in the temperature gradient occurs associated
with sharp variations in <span class="inline-formula"><i>N</i><sup>2</sup></span>. We show the variations in the mean <span class="inline-formula"><i>N</i><sup>2</sup></span>
profiles in coordinates relative to the cold-point tropopause (CPT). A very
thin (<span class="inline-formula"><1</span> km) layer is found with average maximum <span class="inline-formula"><i>N</i><sup>2</sup></span> in the
range of 11.0–<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">12.0</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="42a83e06f816dc8ef2a9245c8dbdfbc8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-6985-2019-ie00001.svg" width="57pt" height="14pt" src="acp-19-6985-2019-ie00001.png"/></svg:svg></span></span> s<span class="inline-formula"><sup>−2</sup></span>. The mean and standard
deviation of TIL sharpness, defined as the difference between the maximum
<span class="inline-formula"><i>N</i><sup>2</sup></span> (<span class="inline-formula">max<i>N</i><sup>2</sup></span>) and minimum <span class="inline-formula"><i>N</i><sup>2</sup></span> (<span class="inline-formula">min<i>N</i><sup>2</sup></span>)
within <span class="inline-formula">±1</span> km of the CPT, is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">10.5</mn><mo>±</mo><mn mathvariant="normal">3.7</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="91pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="275e7873474531cd72599ef6beec5a88"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-6985-2019-ie00002.svg" width="91pt" height="15pt" src="acp-19-6985-2019-ie00002.png"/></svg:svg></span></span> s<span class="inline-formula"><sup>−2</sup></span>. The <span class="inline-formula">max<i>N</i><sup>2</sup></span> is typically located within 0.5 km above CPT.</p>
<p>We focused on the variation in TIL sharpness in two longitude regions,
90–150<span class="inline-formula"><sup>∘</sup></span> E (Maritime Continent; MC) and 170–230<span class="inline-formula"><sup>∘</sup></span> E
(Pacific Ocean; PO), with different land–sea distribution. Seasonal
variations in TIL sharpness and thickness were related to the deep convective
activity represented by low outgoing longwave radiation (OLR) during the
Australian and Asian monsoons. The deviation from the mean sharpness
(sharpness anomaly) was out of phase with the OLR anomaly in both the MC and
PO. The correlation between the sharpness anomaly over the MC and PO and the sea
surface temperature (SST) Niño 3.4 index was <span class="inline-formula">−0.66</span> and <span class="inline-formula">+0.88</span>,
respectively. During La Niña (SST Niño 3.4 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><mo>-</mo><mn mathvariant="normal">0.5</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="096d0bdaad44e76f6a26fa2c658eb838"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-6985-2019-ie00003.svg" width="35pt" height="10pt" src="acp-19-6985-2019-ie00003.png"/></svg:svg></span></span> K) in the MC and
El Niño (SST Niño 3.4 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>></mo><mo>+</mo><mn mathvariant="normal">0.5</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="f29a32addc43628596105d8cfe09bb33"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-6985-2019-ie00004.svg" width="35pt" height="10pt" src="acp-19-6985-2019-ie00004.png"/></svg:svg></span></span> K) in the PO, warmer SSTs in the MC
and PO produce more active deep convection that tends to force the air upward
to the tropopause layer and increase the temperature gradient there. The
intraseasonal variation in sharpness anomaly during slow and fast episodes
of the Madden–Julian Oscillation (MJO) demonstrates that eastward
propagation of the positive sharpness anomaly is associated with organized deep
convection. Deep convection during MJO will tend to decrease <span class="inline-formula"><i>N</i><sup>2</sup></span> below
CPT and increase <span class="inline-formula"><i>N</i><sup>2</sup></span> above CPT, thus enlarging the TIL sharpness. Convective
activity in the tropics is a major control on variations in tropopause
sharpness at intraseasonal to interannual timescales.</p> |
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| ISSN: | 1680-7316 1680-7324 |