New Results on the Midnight Temperature Maximum for mid-

latitudesR. Mesquita(1), J. Meriwether(1), S. Sanders(1), J. Makela(2), D. Fisher(2).

SITE LatitudePARI, NC PAR +35.2°

Virginia Tech, VI VTI +37.2°Eastern Kentucky

Univ., KY EKU +37.8°

Urbana-Champaign, IL UAO +40.1°

Ann Arbor, MI ANN +42.3°

(1) Clemson University, Clemson, SC, United States(rmesqui@clemson.edu);(2) University of Illinois at Urbana-Champaign, Urbana, IL, United States (jmakela@illinois.edu);

MTM detection

To find the MTM in the NATION data sets, we used an algorithm similar to the one published by Martinis et al. (2013)3 for analysis of radar Ti data. The idea is to fit a model to the data to determine the background thermal variation (8-12-24 model) that is subtracted from the data. Then, the residual values are searched for the MTM peak. The function used is given as

(1)

𝑇𝑚𝑜𝑑𝑒𝑙 (𝐿𝑇 )=𝑎0+∑𝑘=1

3

𝑎𝑖cos [ 2𝜋 (𝐿𝑇 −𝑏𝑖 )𝜏 𝑖

];𝜏𝑖 [h ]= [8,12,24 ] .

Introduction

The North American Thermospheric Ionospheric Observing Network (NATION1) has 5 Fabry-Perot interferometers (FPI) operating since 2012 in the locations represented by stars in Figure 1. Table 1 list the coordinates for these sites.

The data products from the NATION network are neutral winds, temperatures, and relative intensity measured with high accuracy at the red line (630-nm) altitude (~250 km).

Figure 3: NATION sites.Figure 2: FPI design

with the sky-scanner.

Figure 1: FPI schematic.

QR1: Link to the figures 1, 2 and 3 explanation.

Table 1: NATION site name, abbreviation, plot color, and latitude, respectively.

In this work we present a new method of searching for the midnight temperature maximum2 peak in the NATION temperature data.

Case Study ExampleThe following NATION plots represent a good example

of a typical MTM night. There is a clear displacement of the MTM peak towards the north and also seen is a significant variation with latitude in the amplitude of the MTM peak relative to the 8-12-24 model.

Figure 6: Typical night of NATION FPI temperature data.

Figure 7: Residuals between the T data and the 8-12-24 model

fit.

Temperatures & ResidualsThe temperature plots shown in this work are from the

NATION data collected in the period of July 2012 to Oct 2013. T values are compared with the 8-12-24 model values to determine the MTM peak amplitude2.

The red dashed horizontal line in Fig. 4 represents 800K, and the scale is 250K for each degree latitude. This line represents the base latitude line of each measurement.

Some MTM evidence is seen in the late night for PAR south, but not much elsewhere.

QR2: Link to the figure 4 explanation.

Figure 4: Typical night of FPI data.

Figure 5: . No Ze, E or W measurements used.

Conclusions• As shown by the results in figures 6 and 10, the algorithm

is effective in detecting both MTM peaks. • The same figures also display MTM northward

propagation.• The new MTM detection technique using the 8-12-24

model fit to determine the thermal background presents high accuracy, being able to successfully find the early night ‘mini-MTM’ signature with peaks as low as 50K.

• A question for future work is the explanation of MTM peak variability observed in this progression with latitude.

Early night MTMAs predicted by WAM [Akmaev et al. (2009)]4 and

reported by Faivre et al. (2006)5 for Arequipa, Peru (-16.2 lat), the early night MTM was successfully observed by our technique combined with the sensitivity of our network.

Figure 8: Adapted from Akmaev et al. (2009)4. Red line at ~250 km. Note peaks at 16 and 24

LT.

Figure 9: Faivre et al. (2005)5. Evidence of early night MTM.

-15-12-9-6-303691215 0 60 120 180 240 300 360

Longitude

Longitude

12 16 20 24 4 8 12Local Time

Figure 10: Sep 23rd 2014 (a) Temperatures and the 8-12-24 model, (b) Residuals.

(a) (b)

4Akmaev, R. A., et al. "Midnight temperature maximum (MTM) in Whole Atmosphere Model (WAM) simulations." (2009);

2Harper, R. M. "Nighttime meridional neutral winds near 350 km at low to mid-latitudes." (1973): 2023-2034;

5Faivre, M., et al. "Climatology of the midnight temperature maximum phenomenon at Arequipa, Peru." Journal of Geophysical Research: Space Physics (1978–2012) 111.A6 (2006);

3Martinis, C., et al. "The midnight temperature maximum from Arecibo incoherent scatter radar ion temperature measurements." (2013);

1Makela, J., et al. "Large-scale measurements of thermospheric dynamics with a multisite Fabry-Perot interferometer network: Overview of plans and results from midlatitude measurements." (2012).