Update comments.

src/mptrac.c

@@ -3004,7 +3004,7 @@ void module_diffusion_pbl(
     tau_u = MAX(tau_u, 300.);
     tau_w = MAX(tau_w, 100.);
 
-    /* Update perturbations (Ryall and Maryon, 1998)... */
+    /* Update perturbations... */
     const double ru = exp(-fabs(dt[ip]) / tau_u);
     const double ru2 = sqrt(1.0 - SQR(ru));
     cache->uvwp[ip][0]
@@ -3018,7 +3018,7 @@ void module_diffusion_pbl(
       = (float) (cache->uvwp[ip][2] * rw + rw2 * rs[3 * ip + 2]
 		 + sig_w * dsigw_dz * dt[ip]);	// TODO: check approx for density correction?
 
-    /* Calculate horizontal mesoscale wind fluctuations... */
+    /* Calculate new air parcel position... */
     atm->lon[ip] += DX2DEG(cache->uvwp[ip][0] * dt[ip] / 1000., atm->lat[ip]);
     atm->lat[ip] += DY2DEG(cache->uvwp[ip][1] * dt[ip] / 1000.);
     atm->p[ip] += DZ2DP(cache->uvwp[ip][2] * dt[ip] / 1000., atm->p[ip]);

src/mptrac.h

@@ -5099,7 +5099,8 @@ void module_diffusion_meso(
  * This function handles the effects of turbulence on particles within
  * the PBL.  It calculates turbulent velocity variances, Lagrangian
  * timescales, and updates particle positions and perturbations based
- * on random fluctuations and boundary layer physics.
+ * on random fluctuations and boundary layer physics. This module adapts
+ * the approach of Ryall and Maryon (1998) and Stohl et al. (2005).
  *
  * @param ctl    Pointer to the control structure containing model settings.
  * @param met0   Pointer to the meteorological data structure for the current timestep.